diff --git a/CHANGELOG.md b/CHANGELOG.md
index e567bef..fde5620 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -80,6 +80,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Expanded `gmail_service.py` unit test coverage: 10 new tests covering `inject_email` HttpError branch, `get_or_create_label` (existing/create/HttpError/generic-error), `inject_debug_email` full flow, `get_refreshed_token` (changed/unchanged), and `service` property lazy initialization — 24 total tests in `test_gmail_service.py`
+- Expanded `api.ts` test coverage from 20% to near-complete: 56 new tests covering all 10 API objects (`authApi`, `userApi`, `mailAccountsApi`, `processingRunsApi`, `gmailApi`, `smtpApi`, `adminApi`, `notificationsApi`, `adminNotificationsApi`, `versionApi`) — 65 total tests in `api.test.ts`
+- Unit tests for `AddMailAccountModal` component (`AddMailAccountModal.test.tsx`): 28 tests covering create/edit mode rendering, provider wizard flow, form field changes, checkbox toggles, auto-detect, test connection, submit mutations, error extraction, and modal close interactions
+- Unit tests for provider endpoints (`test_providers.py`): 23 tests covering provider presets, Gmail credential CRUD, import labels, authorize URL, debug email, and OAuth callback
+- Unit tests for mail account endpoints (`test_mail_accounts.py`): 30 tests covering CRUD, toggle, pull-now, test connection, auto-detect, processing runs, and processing logs
+- Unit tests for authentication endpoints (`test_auth.py`): 22 tests covering register, login, Google OAuth, authorize-url, and helper functions
 - **Backend test coverage expanded** (+150 tests, 361 → 511 total): added `test_gdpr.py` (GDPR masking utilities), `test_gmail_labels.py` (Gmail label helpers), `test_notification_service.py` (Apprise notification service), `test_auth_service.py` (OAuth service token exchange and token creation), `test_version_endpoint.py`, `test_auth_endpoints.py` (register, login, Google OAuth, authorize-url, domain helpers), `test_users_endpoints.py` (profile CRUD, SMTP config upsert/delete), `test_notifications_endpoints.py` (full CRUD + test-send), `test_logs_endpoints.py` (processing-runs pagination/filtering + run log retrieval), and `test_app_settings_endpoints.py` (list, upsert, delete, seed-defaults with bootstrap key guards).
 ## v0.6.1 (2026-04-05)
 
diff --git a/backend/tests/unit/test_auth.py b/backend/tests/unit/test_auth.py
new file mode 100644
index 0000000..bb83e92
--- /dev/null
+++ b/backend/tests/unit/test_auth.py
@@ -0,0 +1,487 @@
+"""
+Unit tests for auth endpoints (backend/app/api/v1/endpoints/auth.py).
+
+All tests mock the database session, security functions, and OAuth service
+so no real PostgreSQL instance or external API is required.
+"""
+
+import pytest
+from datetime import datetime, timezone
+from unittest.mock import AsyncMock, MagicMock, patch
+from urllib.parse import quote as urlquote
+
+from httpx import AsyncClient, ASGITransport
+
+from app.main import create_application
+from app.core.database import get_db
+from app.models.database_models import User, SubscriptionTier
+
+# ── helpers ──────────────────────────────────────────────────────────────
+
+
+def _make_user(**overrides) -> MagicMock:
+    """Return a MagicMock that behaves like a User ORM instance."""
+    defaults = dict(
+        id=1,
+        email="user@example.com",
+        hashed_password="hashedpw",
+        full_name="Test User",
+        is_active=True,
+        is_superuser=False,
+        subscription_tier=SubscriptionTier.FREE,
+        subscription_status="active",
+        google_id=None,
+        oauth_provider=None,
+        last_login_at=None,
+        created_at=datetime.now(timezone.utc),
+        updated_at=datetime.now(timezone.utc),
+        stripe_customer_id=None,
+        stripe_subscription_id=None,
+        subscription_expires_at=None,
+    )
+    defaults.update(overrides)
+    user = MagicMock(spec=User)
+    for k, v in defaults.items():
+        setattr(user, k, v)
+    return user
+
+
+def _scalar_one_or_none(value):
+    """Create a mock result whose .scalar_one_or_none() returns *value*."""
+    result = MagicMock()
+    result.scalar_one_or_none.return_value = value
+    return result
+
+
+def _fake_tokens():
+    return {
+        "access_token": "fake-access-token",
+        "refresh_token": "fake-refresh-token",
+        "token_type": "bearer",
+    }
+
+
+# ── fixtures ─────────────────────────────────────────────────────────────
+
+
+@pytest.fixture
+def app():
+    return create_application()
+
+
+@pytest.fixture
+def mock_db():
+    db = AsyncMock()
+    db.commit = AsyncMock()
+    db.refresh = AsyncMock()
+    db.delete = AsyncMock()
+    db.add = MagicMock()
+    return db
+
+
+@pytest.fixture
+async def client(app, mock_db):
+    """AsyncClient with only get_db overridden (no auth required)."""
+
+    async def _override_db():
+        yield mock_db
+
+    app.dependency_overrides[get_db] = _override_db
+
+    transport = ASGITransport(app=app)
+    async with AsyncClient(transport=transport, base_url="http://test") as c:
+        yield c
+
+    app.dependency_overrides.clear()
+
+
+# ═══════════════════════════════════════════════════════════════════════════
+# Helper functions
+# ═══════════════════════════════════════════════════════════════════════════
+
+
+class TestHelpers:
+    """Unit tests for private helper functions in auth.py."""
+
+    def test_domain_of(self):
+        from app.api.v1.endpoints.auth import _domain_of
+
+        assert _domain_of("alice@Example.COM") == "example.com"
+        assert _domain_of("bob@sub.domain.org") == "sub.domain.org"
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    def test_check_domain_allowed_no_restriction(self, mock_settings):
+        from app.api.v1.endpoints.auth import _check_domain_allowed
+
+        mock_settings.ALLOWED_DOMAINS = []
+        _check_domain_allowed("anyone@whatever.com")  # should not raise
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    def test_check_domain_allowed_passes(self, mock_settings):
+        from app.api.v1.endpoints.auth import _check_domain_allowed
+
+        mock_settings.ALLOWED_DOMAINS = ["acme.com"]
+        _check_domain_allowed("alice@acme.com")  # should not raise
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    def test_check_domain_allowed_blocks(self, mock_settings):
+        from fastapi import HTTPException
+
+        from app.api.v1.endpoints.auth import _check_domain_allowed
+
+        mock_settings.ALLOWED_DOMAINS = ["acme.com"]
+        with pytest.raises(HTTPException) as exc_info:
+            _check_domain_allowed("alice@blocked.com")
+        assert exc_info.value.status_code == 403
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    def test_default_tier_valid(self, mock_settings):
+        from app.api.v1.endpoints.auth import _default_tier
+
+        mock_settings.DEFAULT_USER_TIER = "pro"
+        assert _default_tier() == SubscriptionTier.PRO
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    def test_default_tier_invalid_falls_back(self, mock_settings):
+        from app.api.v1.endpoints.auth import _default_tier
+
+        mock_settings.DEFAULT_USER_TIER = "invalid_tier"
+        assert _default_tier() == SubscriptionTier.FREE
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    def test_is_admin_email_match(self, mock_settings):
+        from app.api.v1.endpoints.auth import _is_admin_email
+
+        mock_settings.ADMIN_EMAIL = "Admin@Example.com"
+        assert _is_admin_email("admin@example.com") is True
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    def test_is_admin_email_no_match(self, mock_settings):
+        from app.api.v1.endpoints.auth import _is_admin_email
+
+        mock_settings.ADMIN_EMAIL = "admin@example.com"
+        assert _is_admin_email("other@example.com") is False
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    def test_is_admin_email_none(self, mock_settings):
+        from app.api.v1.endpoints.auth import _is_admin_email
+
+        mock_settings.ADMIN_EMAIL = None
+        assert _is_admin_email("anyone@example.com") is False
+
+
+# ═══════════════════════════════════════════════════════════════════════════
+# POST /api/v1/auth/register
+# ═══════════════════════════════════════════════════════════════════════════
+
+
+class TestRegister:
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    @patch("app.api.v1.endpoints.auth.get_password_hash", return_value="hashed123")
+    async def test_register_success(self, _mock_hash, mock_settings, client, mock_db):
+        mock_settings.ALLOWED_DOMAINS = []
+        mock_settings.DEFAULT_USER_TIER = "free"
+        mock_settings.ADMIN_EMAIL = None
+
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        # Simulate db.refresh assigning an id and required fields
+        def _set_id(obj):
+            obj.id = 42
+            obj.email = "new@example.com"
+            obj.full_name = "New User"
+            obj.is_active = True
+            obj.subscription_tier = SubscriptionTier.FREE
+            obj.subscription_status = "active"
+            obj.created_at = datetime.now(timezone.utc)
+
+        mock_db.refresh = AsyncMock(side_effect=_set_id)
+
+        resp = await client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": "new@example.com",
+                "full_name": "New User",
+                "password": "secret",
+            },
+        )
+
+        assert resp.status_code == 201
+        body = resp.json()
+        assert body["email"] == "new@example.com"
+        assert body["id"] == 42
+        mock_db.add.assert_called_once()
+        mock_db.commit.assert_awaited_once()
+
+    async def test_register_duplicate_email(self, client, mock_db):
+        existing = _make_user(email="dup@example.com")
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(existing))
+
+        resp = await client.post(
+            "/api/v1/auth/register",
+            json={"email": "dup@example.com", "full_name": "Dup", "password": "pw"},
+        )
+
+        assert resp.status_code == 400
+        assert "already registered" in resp.json()["detail"]
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    async def test_register_domain_restricted(self, mock_settings, client, mock_db):
+        mock_settings.ALLOWED_DOMAINS = ["acme.com"]
+
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await client.post(
+            "/api/v1/auth/register",
+            json={
+                "email": "user@blocked.com",
+                "full_name": "Blocked",
+                "password": "pw",
+            },
+        )
+
+        assert resp.status_code == 403
+        assert "not authorised" in resp.json()["detail"]
+
+
+# ═══════════════════════════════════════════════════════════════════════════
+# POST /api/v1/auth/login
+# ═══════════════════════════════════════════════════════════════════════════
+
+
+class TestLogin:
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    @patch(
+        "app.api.v1.endpoints.auth.oauth_service.create_tokens_for_user",
+        return_value=_fake_tokens(),
+    )
+    @patch("app.api.v1.endpoints.auth.verify_password", return_value=True)
+    async def test_login_success(
+        self, _mock_verify, _mock_tokens, mock_settings, client, mock_db
+    ):
+        mock_settings.ALLOWED_DOMAINS = []
+        mock_settings.ADMIN_EMAIL = None
+
+        user = _make_user(email="login@example.com")
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(user))
+
+        resp = await client.post(
+            "/api/v1/auth/login",
+            data={"username": "login@example.com", "password": "correct"},
+        )
+
+        assert resp.status_code == 200
+        body = resp.json()
+        assert body["access_token"] == "fake-access-token"
+        assert body["token_type"] == "bearer"
+        mock_db.commit.assert_awaited_once()
+
+    @patch("app.api.v1.endpoints.auth.verify_password", return_value=False)
+    async def test_login_user_not_found(self, _mock_verify, client, mock_db):
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await client.post(
+            "/api/v1/auth/login",
+            data={"username": "nobody@example.com", "password": "pw"},
+        )
+
+        assert resp.status_code == 401
+        assert "Incorrect email or password" in resp.json()["detail"]
+
+    @patch("app.api.v1.endpoints.auth.verify_password", return_value=False)
+    async def test_login_wrong_password(self, _mock_verify, client, mock_db):
+        user = _make_user(email="login@example.com")
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(user))
+
+        resp = await client.post(
+            "/api/v1/auth/login",
+            data={"username": "login@example.com", "password": "wrong"},
+        )
+
+        assert resp.status_code == 401
+        assert "Incorrect email or password" in resp.json()["detail"]
+
+    @patch("app.api.v1.endpoints.auth.verify_password", return_value=True)
+    async def test_login_inactive_user(self, _mock_verify, client, mock_db):
+        user = _make_user(email="inactive@example.com", is_active=False)
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(user))
+
+        resp = await client.post(
+            "/api/v1/auth/login",
+            data={"username": "inactive@example.com", "password": "pw"},
+        )
+
+        assert resp.status_code == 403
+        assert "inactive" in resp.json()["detail"]
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    @patch(
+        "app.api.v1.endpoints.auth.oauth_service.create_tokens_for_user",
+        return_value=_fake_tokens(),
+    )
+    @patch("app.api.v1.endpoints.auth.verify_password", return_value=True)
+    async def test_login_admin_auto_promotion(
+        self, _mock_verify, _mock_tokens, mock_settings, client, mock_db
+    ):
+        mock_settings.ALLOWED_DOMAINS = []
+        mock_settings.ADMIN_EMAIL = "admin@example.com"
+
+        user = _make_user(email="admin@example.com", is_superuser=False, is_active=True)
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(user))
+
+        resp = await client.post(
+            "/api/v1/auth/login",
+            data={"username": "admin@example.com", "password": "pw"},
+        )
+
+        assert resp.status_code == 200
+        # The endpoint should have set is_superuser = True on the user mock
+        assert user.is_superuser is True
+
+
+# ═══════════════════════════════════════════════════════════════════════════
+# POST /api/v1/auth/google
+# ═══════════════════════════════════════════════════════════════════════════
+
+
+class TestGoogleOAuth:
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    @patch(
+        "app.api.v1.endpoints.auth.oauth_service.create_tokens_for_user",
+        return_value=_fake_tokens(),
+    )
+    @patch("app.api.v1.endpoints.auth.oauth_service.get_google_user_info")
+    async def test_google_existing_user(
+        self, mock_google_info, _mock_tokens, mock_settings, client, mock_db
+    ):
+        mock_settings.ALLOWED_DOMAINS = []
+        mock_settings.ADMIN_EMAIL = None
+
+        mock_google_info.return_value = {
+            "email": "existing@example.com",
+            "google_id": "g-123",
+            "full_name": "Existing User",
+            "verified_email": True,
+        }
+
+        user = _make_user(email="existing@example.com", google_id="g-123")
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(user))
+
+        resp = await client.post(
+            "/api/v1/auth/google",
+            json={"code": "auth-code", "redirect_uri": "http://localhost/callback"},
+        )
+
+        assert resp.status_code == 200
+        body = resp.json()
+        assert body["access_token"] == "fake-access-token"
+        mock_db.commit.assert_awaited_once()
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    @patch(
+        "app.api.v1.endpoints.auth.oauth_service.create_tokens_for_user",
+        return_value=_fake_tokens(),
+    )
+    @patch("app.api.v1.endpoints.auth.oauth_service.get_google_user_info")
+    async def test_google_new_user(
+        self, mock_google_info, _mock_tokens, mock_settings, client, mock_db
+    ):
+        mock_settings.ALLOWED_DOMAINS = []
+        mock_settings.DEFAULT_USER_TIER = "free"
+        mock_settings.ADMIN_EMAIL = None
+
+        mock_google_info.return_value = {
+            "email": "brand-new@example.com",
+            "google_id": "g-456",
+            "full_name": "Brand New",
+            "verified_email": True,
+        }
+
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        def _set_id(obj):
+            obj.id = 99
+
+        mock_db.refresh = AsyncMock(side_effect=_set_id)
+
+        resp = await client.post(
+            "/api/v1/auth/google",
+            json={"code": "auth-code", "redirect_uri": "http://localhost/callback"},
+        )
+
+        assert resp.status_code == 200
+        body = resp.json()
+        assert body["access_token"] == "fake-access-token"
+        mock_db.add.assert_called_once()
+
+    @patch("app.api.v1.endpoints.auth.oauth_service.get_google_user_info")
+    async def test_google_email_not_verified(self, mock_google_info, client, mock_db):
+        mock_google_info.return_value = {
+            "email": "unverified@example.com",
+            "google_id": "g-789",
+            "verified_email": False,
+        }
+
+        resp = await client.post(
+            "/api/v1/auth/google",
+            json={"code": "auth-code", "redirect_uri": "http://localhost/callback"},
+        )
+
+        assert resp.status_code == 400
+        assert "not verified" in resp.json()["detail"]
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    @patch("app.api.v1.endpoints.auth.oauth_service.get_google_user_info")
+    async def test_google_domain_restricted_new_user(
+        self, mock_google_info, mock_settings, client, mock_db
+    ):
+        mock_settings.ALLOWED_DOMAINS = ["acme.com"]
+        mock_settings.DEFAULT_USER_TIER = "free"
+        mock_settings.ADMIN_EMAIL = None
+
+        mock_google_info.return_value = {
+            "email": "person@blocked.com",
+            "google_id": "g-block",
+            "full_name": "Blocked",
+            "verified_email": True,
+        }
+
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await client.post(
+            "/api/v1/auth/google",
+            json={"code": "auth-code", "redirect_uri": "http://localhost/callback"},
+        )
+
+        assert resp.status_code == 403
+        assert "not authorised" in resp.json()["detail"]
+
+
+# ═══════════════════════════════════════════════════════════════════════════
+# GET /api/v1/auth/google/authorize-url
+# ═══════════════════════════════════════════════════════════════════════════
+
+
+class TestGoogleAuthorizeUrl:
+
+    @patch("app.api.v1.endpoints.auth.settings")
+    async def test_returns_correct_url(self, mock_settings, client):
+        mock_settings.GOOGLE_CLIENT_ID = "test-client-id"
+
+        resp = await client.get(
+            "/api/v1/auth/google/authorize-url",
+            params={"redirect_uri": "http://localhost:3000/callback"},
+        )
+
+        assert resp.status_code == 200
+        body = resp.json()
+        url = body["authorization_url"]
+        assert "accounts.google.com" in url
+        assert "client_id=test-client-id" in url
+        assert "redirect_uri=http://localhost:3000/callback" in url
+        expected_scope = urlquote("openid email profile")
+        assert f"scope={expected_scope}" in url
+        assert "prompt=select_account" in url
diff --git a/backend/tests/unit/test_gmail_service.py b/backend/tests/unit/test_gmail_service.py
index 4289104..31a582b 100644
--- a/backend/tests/unit/test_gmail_service.py
+++ b/backend/tests/unit/test_gmail_service.py
@@ -2,8 +2,13 @@
 Unit tests for Gmail service module.
 """
 
+import json
+from datetime import datetime, timezone
+from unittest.mock import AsyncMock, MagicMock, patch
+
 import pytest
-from unittest.mock import AsyncMock, MagicMock
+from googleapiclient.errors import HttpError
+
 from app.services.gmail_service import GmailService, GmailInjectionError, GMAIL_SCOPES
 from app.utils.gmail_labels import (
     DEFAULT_IMPORT_LABEL_TEMPLATES,
@@ -202,3 +207,215 @@ class TestGmailService:
         )
 
         assert label_ids == ["INBOX", "Label-source", "Label-imported"]
+
+    # ------------------------------------------------------------------
+    # Helper for HttpError construction
+    # ------------------------------------------------------------------
+    @staticmethod
+    def _make_http_error(
+        status_code: int = 401, reason: str = "Unauthorized"
+    ) -> HttpError:
+        resp = MagicMock()
+        resp.status = status_code
+        resp.reason = reason
+        content = json.dumps({"error": {"message": reason}}).encode()
+        return HttpError(resp, content, uri="https://gmail.googleapis.com/test")
+
+    # ------------------------------------------------------------------
+    # inject_email – HttpError branch
+    # ------------------------------------------------------------------
+    @pytest.mark.asyncio
+    async def test_inject_email_http_error(self):
+        """HttpError in inject_email is caught and re-raised as GmailInjectionError."""
+        service = GmailService(access_token="test-access-token")
+
+        mock_api = MagicMock()
+        mock_api.users().messages().insert().execute.side_effect = (
+            self._make_http_error(403, "Forbidden")
+        )
+        service._service = mock_api
+
+        with pytest.raises(GmailInjectionError, match="Gmail API error"):
+            await service.inject_email(
+                raw_email=b"From: a@b.com\r\nSubject: X\r\n\r\nBody",
+            )
+
+    # ------------------------------------------------------------------
+    # get_or_create_label – existing label found
+    # ------------------------------------------------------------------
+    @pytest.mark.asyncio
+    async def test_get_or_create_label_existing(self):
+        """Returns ID of an existing label matched case-insensitively."""
+        service = GmailService(access_token="test-access-token")
+
+        mock_api = MagicMock()
+        mock_api.users().labels().list().execute.return_value = {
+            "labels": [
+                {"id": "Label_1", "name": "imported"},
+                {"id": "INBOX", "name": "INBOX"},
+            ]
+        }
+        service._service = mock_api
+
+        label_id = await service.get_or_create_label("Imported")
+        assert label_id == "Label_1"
+
+    # ------------------------------------------------------------------
+    # get_or_create_label – label not found, creates new one
+    # ------------------------------------------------------------------
+    @pytest.mark.asyncio
+    async def test_get_or_create_label_creates_new(self):
+        """Creates a new label when no existing label matches."""
+        service = GmailService(access_token="test-access-token")
+
+        mock_api = MagicMock()
+        mock_api.users().labels().list().execute.return_value = {
+            "labels": [{"id": "INBOX", "name": "INBOX"}]
+        }
+        mock_api.users().labels().create().execute.return_value = {
+            "id": "Label_new",
+            "name": "new-label",
+        }
+        service._service = mock_api
+
+        label_id = await service.get_or_create_label("new-label")
+        assert label_id == "Label_new"
+
+    # ------------------------------------------------------------------
+    # get_or_create_label – HttpError handling
+    # ------------------------------------------------------------------
+    @pytest.mark.asyncio
+    async def test_get_or_create_label_http_error(self):
+        """HttpError during label list raises GmailInjectionError."""
+        service = GmailService(access_token="test-access-token")
+
+        mock_api = MagicMock()
+        mock_api.users().labels().list().execute.side_effect = self._make_http_error(
+            500, "Internal Server Error"
+        )
+        service._service = mock_api
+
+        with pytest.raises(GmailInjectionError, match="Gmail API error"):
+            await service.get_or_create_label("test")
+
+    # ------------------------------------------------------------------
+    # get_or_create_label – generic Exception handling
+    # ------------------------------------------------------------------
+    @pytest.mark.asyncio
+    async def test_get_or_create_label_generic_exception(self):
+        """Generic exception during label management raises GmailInjectionError."""
+        service = GmailService(access_token="test-access-token")
+
+        mock_api = MagicMock()
+        mock_api.users().labels().list().execute.side_effect = RuntimeError("boom")
+        service._service = mock_api
+
+        with pytest.raises(GmailInjectionError, match="Failed to get/create"):
+            await service.get_or_create_label("oops")
+
+    # ------------------------------------------------------------------
+    # inject_debug_email – full flow
+    # ------------------------------------------------------------------
+    @pytest.mark.asyncio
+    async def test_inject_debug_email(self):
+        """inject_debug_email creates labels and injects a test email."""
+        service = GmailService(access_token="test-access-token")
+
+        service.build_import_label_ids = AsyncMock(  # type: ignore[method-assign]
+            return_value=["INBOX", "Label_imported"]
+        )
+        service.get_or_create_label = AsyncMock(  # type: ignore[method-assign]
+            return_value="Label_test"
+        )
+        service.inject_email = AsyncMock(  # type: ignore[method-assign]
+            return_value={
+                "message_id": "msg1",
+                "thread_id": "t1",
+                "label_ids": ["INBOX", "Label_imported", "Label_test"],
+            }
+        )
+
+        result = await service.inject_debug_email("user@gmail.com")
+
+        assert result["message_id"] == "msg1"
+        assert "Label_test" in result["label_ids"]
+        service.build_import_label_ids.assert_awaited_once()
+        service.get_or_create_label.assert_awaited_once_with("test")
+        service.inject_email.assert_awaited_once()
+        # The test label should have been appended to label_ids
+        call_kwargs = service.inject_email.call_args
+        assert "Label_test" in call_kwargs.kwargs["label_ids"]
+
+    # ------------------------------------------------------------------
+    # inject_debug_email – test label already present in import labels
+    # ------------------------------------------------------------------
+    @pytest.mark.asyncio
+    async def test_inject_debug_email_test_label_already_present(self):
+        """inject_debug_email does not duplicate the test label."""
+        service = GmailService(access_token="test-access-token")
+
+        service.build_import_label_ids = AsyncMock(  # type: ignore[method-assign]
+            return_value=["INBOX", "Label_test"]
+        )
+        service.get_or_create_label = AsyncMock(  # type: ignore[method-assign]
+            return_value="Label_test"
+        )
+        service.inject_email = AsyncMock(  # type: ignore[method-assign]
+            return_value={
+                "message_id": "msg2",
+                "thread_id": "t2",
+                "label_ids": ["INBOX", "Label_test"],
+            }
+        )
+
+        result = await service.inject_debug_email("user@gmail.com")
+
+        assert result["message_id"] == "msg2"
+        call_kwargs = service.inject_email.call_args
+        # Label_test should appear only once
+        assert call_kwargs.kwargs["label_ids"].count("Label_test") == 1
+
+    # ------------------------------------------------------------------
+    # get_refreshed_token – token was NOT refreshed
+    # ------------------------------------------------------------------
+    def test_get_refreshed_token_no_change(self):
+        """Returns None when the token has not changed."""
+        service = GmailService(access_token="original-token")
+        assert service.get_refreshed_token() is None
+
+    # ------------------------------------------------------------------
+    # get_refreshed_token – token was refreshed
+    # ------------------------------------------------------------------
+    def test_get_refreshed_token_changed(self):
+        """Returns new token info when the token was refreshed."""
+        service = GmailService(access_token="original-token")
+
+        # Simulate an automatic token refresh by mutating credentials
+        new_expiry = datetime(2099, 1, 1, tzinfo=timezone.utc)
+        service.credentials.token = "new-refreshed-token"
+        service.credentials.expiry = new_expiry
+
+        result = service.get_refreshed_token()
+        assert result is not None
+        assert result["access_token"] == "new-refreshed-token"
+        assert result["expiry"] == new_expiry
+
+    # ------------------------------------------------------------------
+    # service property – lazy init builds the service
+    # ------------------------------------------------------------------
+    def test_service_property_builds_service(self):
+        """Accessing .service triggers googleapiclient.discovery.build."""
+        with patch("app.services.gmail_service.build") as mock_build:
+            mock_build.return_value = MagicMock()
+            service = GmailService(access_token="test-access-token")
+            assert service._service is None
+
+            api = service.service  # trigger lazy init
+
+            mock_build.assert_called_once_with(
+                "gmail", "v1", credentials=service.credentials, cache_discovery=False
+            )
+            assert api is mock_build.return_value
+            # Second access should NOT call build again
+            _ = service.service
+            mock_build.assert_called_once()
diff --git a/backend/tests/unit/test_mail_accounts.py b/backend/tests/unit/test_mail_accounts.py
new file mode 100644
index 0000000..d3e5ef5
--- /dev/null
+++ b/backend/tests/unit/test_mail_accounts.py
@@ -0,0 +1,774 @@
+"""
+Unit tests for mail account endpoints (backend/app/api/v1/endpoints/mail_accounts.py).
+
+All tests mock the database session and auth dependencies so no real
+PostgreSQL instance is required.
+"""
+
+import pytest
+from datetime import datetime, timezone
+from unittest.mock import AsyncMock, MagicMock, patch
+
+from httpx import AsyncClient, ASGITransport
+
+from app.main import create_application
+from app.core.database import get_db
+from app.core.deps import get_current_active_user
+from app.models.database_models import (
+    User,
+    MailAccount,
+    ProcessingRun,
+    ProcessingLog,
+    SubscriptionPlan,
+    SubscriptionTier,
+    AccountStatus,
+)
+
+BASE = "/api/v1/mail-accounts"
+
+# ── helpers ──────────────────────────────────────────────────────────────
+
+
+def _make_user(**overrides) -> MagicMock:
+    """Return a MagicMock that behaves like a User ORM instance."""
+    defaults = dict(
+        id=1,
+        email="user@example.com",
+        hashed_password="hashed",
+        full_name="Test User",
+        is_active=True,
+        is_superuser=False,
+        subscription_tier=SubscriptionTier.FREE,
+        subscription_status="active",
+        google_id=None,
+        oauth_provider=None,
+        last_login_at=None,
+        created_at=datetime.now(timezone.utc),
+        updated_at=datetime.now(timezone.utc),
+        stripe_customer_id=None,
+        stripe_subscription_id=None,
+        subscription_expires_at=None,
+    )
+    defaults.update(overrides)
+    user = MagicMock(spec=User)
+    for k, v in defaults.items():
+        setattr(user, k, v)
+    return user
+
+
+def _make_superuser(**overrides) -> MagicMock:
+    return _make_user(is_superuser=True, **overrides)
+
+
+def _make_account(**overrides) -> MagicMock:
+    """Return a MagicMock that behaves like a MailAccount ORM instance."""
+    defaults = dict(
+        id=10,
+        user_id=1,
+        name="Test Account",
+        email_address="test@example.com",
+        protocol="pop3_ssl",
+        host="pop.example.com",
+        port=995,
+        use_ssl=True,
+        use_tls=False,
+        username="test@example.com",
+        encrypted_password="encrypted_pass",
+        forward_to="me@gmail.com",
+        delivery_method="gmail_api",
+        status="active",
+        is_enabled=True,
+        check_interval_minutes=5,
+        max_emails_per_check=50,
+        delete_after_forward=True,
+        provider_name="Gmail",
+        auto_detected=False,
+        total_emails_processed=100,
+        total_emails_failed=2,
+        last_check_at=datetime.now(timezone.utc),
+        last_successful_check_at=datetime.now(timezone.utc),
+        last_error_at=None,
+        last_error_message=None,
+        created_at=datetime.now(timezone.utc),
+        updated_at=datetime.now(timezone.utc),
+    )
+    defaults.update(overrides)
+    account = MagicMock(spec=MailAccount)
+    for k, v in defaults.items():
+        setattr(account, k, v)
+    return account
+
+
+def _make_run(**overrides) -> MagicMock:
+    """Return a MagicMock that behaves like a ProcessingRun ORM instance."""
+    defaults = dict(
+        id=100,
+        mail_account_id=10,
+        started_at=datetime.now(timezone.utc),
+        completed_at=datetime.now(timezone.utc),
+        duration_seconds=1.5,
+        emails_fetched=5,
+        emails_forwarded=4,
+        emails_failed=1,
+        status="completed",
+        error_message=None,
+    )
+    defaults.update(overrides)
+    run = MagicMock(spec=ProcessingRun)
+    for k, v in defaults.items():
+        setattr(run, k, v)
+    return run
+
+
+def _make_log(**overrides) -> MagicMock:
+    """Return a MagicMock that behaves like a ProcessingLog ORM instance."""
+    defaults = dict(
+        id=200,
+        user_id=1,
+        mail_account_id=10,
+        processing_run_id=100,
+        timestamp=datetime.now(timezone.utc),
+        level="INFO",
+        message="Processed email",
+        email_subject="Hello",
+        email_from="sender@example.com",
+        email_size_bytes=1024,
+        success=True,
+        error_details=None,
+    )
+    defaults.update(overrides)
+    log = MagicMock(spec=ProcessingLog)
+    for k, v in defaults.items():
+        setattr(log, k, v)
+    return log
+
+
+def _scalar_one_or_none(value):
+    """Create a mock result whose .scalar_one_or_none() returns *value*."""
+    result = MagicMock()
+    result.scalar_one_or_none.return_value = value
+    return result
+
+
+def _scalar_one(value):
+    result = MagicMock()
+    result.scalar_one.return_value = value
+    return result
+
+
+def _scalars_all(values):
+    result = MagicMock()
+    scalars = MagicMock()
+    scalars.all.return_value = values
+    result.scalars.return_value = scalars
+    return result
+
+
+# ── fixtures ─────────────────────────────────────────────────────────────
+
+
+@pytest.fixture
+def app():
+    return create_application()
+
+
+@pytest.fixture
+def regular_user():
+    return _make_user()
+
+
+@pytest.fixture
+def superuser():
+    return _make_superuser()
+
+
+@pytest.fixture
+def mock_db():
+    db = AsyncMock()
+    db.commit = AsyncMock()
+    db.refresh = AsyncMock()
+    db.delete = AsyncMock()
+    db.add = MagicMock()
+    return db
+
+
+@pytest.fixture
+async def client(app, regular_user, mock_db):
+    """AsyncClient where the caller is a regular user and db is mocked."""
+
+    async def _override_user():
+        return regular_user
+
+    async def _override_db():
+        yield mock_db
+
+    app.dependency_overrides[get_current_active_user] = _override_user
+    app.dependency_overrides[get_db] = _override_db
+
+    transport = ASGITransport(app=app)
+    async with AsyncClient(transport=transport, base_url="http://test") as c:
+        yield c
+
+    app.dependency_overrides.clear()
+
+
+@pytest.fixture
+async def superuser_client(app, superuser, mock_db):
+    """AsyncClient where the caller is a superuser and db is mocked."""
+
+    async def _override_user():
+        return superuser
+
+    async def _override_db():
+        yield mock_db
+
+    app.dependency_overrides[get_current_active_user] = _override_user
+    app.dependency_overrides[get_db] = _override_db
+
+    transport = ASGITransport(app=app)
+    async with AsyncClient(transport=transport, base_url="http://test") as c:
+        yield c
+
+    app.dependency_overrides.clear()
+
+
+# ── account payload helper ───────────────────────────────────────────────
+
+VALID_ACCOUNT_PAYLOAD = dict(
+    name="My Account",
+    email_address="inbox@example.com",
+    protocol="pop3_ssl",
+    host="pop.example.com",
+    port=995,
+    use_ssl=True,
+    use_tls=False,
+    username="inbox@example.com",
+    password="secret",
+    forward_to="me@gmail.com",
+    delivery_method="gmail_api",
+    is_enabled=True,
+    check_interval_minutes=5,
+    max_emails_per_check=50,
+    delete_after_forward=True,
+    provider_name="Gmail",
+)
+
+
+# ── tests: create mail account ──────────────────────────────────────────
+
+
+class TestCreateMailAccount:
+    """POST /api/v1/mail-accounts"""
+
+    @patch("app.api.v1.endpoints.mail_accounts.encrypt_credential", return_value="enc")
+    async def test_create_superuser_bypasses_limit(
+        self, mock_encrypt, superuser_client, mock_db
+    ):
+        """Superusers skip the subscription-limit check entirely."""
+        mock_db.refresh = AsyncMock(side_effect=lambda obj: None)
+        created = {}
+
+        def capture_add(obj):
+            created["obj"] = obj
+            # Give the added object all the response fields
+            for k, v in {
+                "id": 10,
+                "user_id": 1,
+                "status": "active",
+                "auto_detected": False,
+                "total_emails_processed": 0,
+                "total_emails_failed": 0,
+                "last_check_at": None,
+                "last_successful_check_at": None,
+                "last_error_at": None,
+                "last_error_message": None,
+                "created_at": datetime.now(timezone.utc),
+                "updated_at": datetime.now(timezone.utc),
+            }.items():
+                setattr(obj, k, v)
+
+        mock_db.add = MagicMock(side_effect=capture_add)
+
+        resp = await superuser_client.post(BASE, json=VALID_ACCOUNT_PAYLOAD)
+        assert resp.status_code == 201
+        data = resp.json()
+        assert data["name"] == "My Account"
+        assert data["email_address"] == "inbox@example.com"
+        mock_encrypt.assert_called_once_with("secret")
+        mock_db.commit.assert_called_once()
+
+    @patch("app.api.v1.endpoints.mail_accounts.encrypt_credential", return_value="enc")
+    async def test_create_regular_user_within_limit(
+        self, mock_encrypt, client, mock_db
+    ):
+        """Regular user under their plan limit can create an account."""
+        # 1st execute: count existing accounts (returns 0 accounts)
+        # 2nd execute: fetch subscription plan
+        plan = MagicMock(spec=SubscriptionPlan)
+        plan.max_mail_accounts = 5
+
+        mock_db.execute = AsyncMock(
+            side_effect=[
+                _scalars_all([]),  # existing accounts
+                _scalar_one_or_none(plan),  # subscription plan
+            ]
+        )
+
+        def capture_add(obj):
+            for k, v in {
+                "id": 10,
+                "user_id": 1,
+                "status": "active",
+                "auto_detected": False,
+                "total_emails_processed": 0,
+                "total_emails_failed": 0,
+                "last_check_at": None,
+                "last_successful_check_at": None,
+                "last_error_at": None,
+                "last_error_message": None,
+                "created_at": datetime.now(timezone.utc),
+                "updated_at": datetime.now(timezone.utc),
+            }.items():
+                setattr(obj, k, v)
+
+        mock_db.add = MagicMock(side_effect=capture_add)
+
+        resp = await client.post(BASE, json=VALID_ACCOUNT_PAYLOAD)
+        assert resp.status_code == 201
+        mock_encrypt.assert_called_once_with("secret")
+
+    @patch("app.api.v1.endpoints.mail_accounts.encrypt_credential", return_value="enc")
+    async def test_create_subscription_limit_reached(
+        self, mock_encrypt, client, mock_db
+    ):
+        """402 when account limit is reached."""
+        existing = [_make_account(id=i) for i in range(1)]
+        plan = MagicMock(spec=SubscriptionPlan)
+        plan.max_mail_accounts = 1
+
+        mock_db.execute = AsyncMock(
+            side_effect=[
+                _scalars_all(existing),  # existing accounts (1 already)
+                _scalar_one_or_none(plan),  # plan says max=1
+            ]
+        )
+
+        resp = await client.post(BASE, json=VALID_ACCOUNT_PAYLOAD)
+        assert resp.status_code == 402
+        assert "limit" in resp.json()["detail"].lower()
+
+    @patch("app.api.v1.endpoints.mail_accounts.encrypt_credential", return_value="enc")
+    async def test_create_uses_db_plan_limit(self, mock_encrypt, client, mock_db):
+        """When a SubscriptionPlan exists in the DB, use its max_mail_accounts."""
+        plan = MagicMock(spec=SubscriptionPlan)
+        plan.max_mail_accounts = 3
+
+        existing = [_make_account(id=i) for i in range(3)]
+        mock_db.execute = AsyncMock(
+            side_effect=[
+                _scalars_all(existing),  # 3 existing
+                _scalar_one_or_none(plan),  # plan limit = 3
+            ]
+        )
+
+        resp = await client.post(BASE, json=VALID_ACCOUNT_PAYLOAD)
+        assert resp.status_code == 402
+
+    @patch("app.api.v1.endpoints.mail_accounts.encrypt_credential", return_value="enc")
+    async def test_create_fallback_tier_limit_when_no_plan(
+        self, mock_encrypt, client, mock_db
+    ):
+        """When no SubscriptionPlan row exists, falls back to settings tier limits."""
+        mock_db.execute = AsyncMock(
+            side_effect=[
+                _scalars_all([]),  # 0 existing accounts
+                _scalar_one_or_none(None),  # no plan in DB → fallback
+            ]
+        )
+
+        def capture_add(obj):
+            for k, v in {
+                "id": 10,
+                "user_id": 1,
+                "status": "active",
+                "auto_detected": False,
+                "total_emails_processed": 0,
+                "total_emails_failed": 0,
+                "last_check_at": None,
+                "last_successful_check_at": None,
+                "last_error_at": None,
+                "last_error_message": None,
+                "created_at": datetime.now(timezone.utc),
+                "updated_at": datetime.now(timezone.utc),
+            }.items():
+                setattr(obj, k, v)
+
+        mock_db.add = MagicMock(side_effect=capture_add)
+
+        resp = await client.post(BASE, json=VALID_ACCOUNT_PAYLOAD)
+        # free tier default is 1, and 0 existing → should succeed
+        assert resp.status_code == 201
+
+
+# ── tests: list mail accounts ───────────────────────────────────────────
+
+
+class TestListMailAccounts:
+    """GET /api/v1/mail-accounts"""
+
+    async def test_list_accounts(self, client, mock_db):
+        accounts = [_make_account(id=1), _make_account(id=2)]
+        mock_db.execute = AsyncMock(return_value=_scalars_all(accounts))
+
+        resp = await client.get(BASE)
+        assert resp.status_code == 200
+        data = resp.json()
+        assert len(data) == 2
+
+
+# ── tests: get mail account ─────────────────────────────────────────────
+
+
+class TestGetMailAccount:
+    """GET /api/v1/mail-accounts/{account_id}"""
+
+    async def test_get_account_success(self, client, mock_db):
+        account = _make_account()
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(account))
+
+        resp = await client.get(f"{BASE}/10")
+        assert resp.status_code == 200
+        assert resp.json()["id"] == 10
+
+    async def test_get_account_not_found(self, client, mock_db):
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await client.get(f"{BASE}/999")
+        assert resp.status_code == 404
+
+
+# ── tests: update mail account ──────────────────────────────────────────
+
+
+class TestUpdateMailAccount:
+    """PUT /api/v1/mail-accounts/{account_id}"""
+
+    async def test_update_account_success(self, client, mock_db):
+        account = _make_account()
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(account))
+
+        resp = await client.put(f"{BASE}/10", json={"name": "Updated Name"})
+        assert resp.status_code == 200
+        mock_db.commit.assert_called()
+
+    @patch(
+        "app.api.v1.endpoints.mail_accounts.encrypt_credential", return_value="new_enc"
+    )
+    async def test_update_account_with_password(self, mock_encrypt, client, mock_db):
+        account = _make_account()
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(account))
+
+        resp = await client.put(f"{BASE}/10", json={"password": "newpass"})
+        assert resp.status_code == 200
+        mock_encrypt.assert_called_once_with("newpass")
+        # Verify encrypted_password was set on the account
+        assert account.encrypted_password == "new_enc"
+
+    async def test_update_account_not_found(self, client, mock_db):
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await client.put(f"{BASE}/999", json={"name": "X"})
+        assert resp.status_code == 404
+
+
+# ── tests: delete mail account ──────────────────────────────────────────
+
+
+class TestDeleteMailAccount:
+    """DELETE /api/v1/mail-accounts/{account_id}"""
+
+    async def test_delete_account_success(self, client, mock_db):
+        account = _make_account()
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(account))
+
+        resp = await client.delete(f"{BASE}/10")
+        assert resp.status_code == 204
+        mock_db.delete.assert_called_once_with(account)
+        mock_db.commit.assert_called()
+
+    async def test_delete_account_not_found(self, client, mock_db):
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await client.delete(f"{BASE}/999")
+        assert resp.status_code == 404
+
+
+# ── tests: toggle mail account ──────────────────────────────────────────
+
+
+class TestToggleMailAccount:
+    """PATCH /api/v1/mail-accounts/{account_id}/toggle"""
+
+    async def test_toggle_enable_resets_error(self, client, mock_db):
+        """Toggling an ERROR account to enabled resets status to ACTIVE."""
+        account = _make_account(is_enabled=False, status=AccountStatus.ERROR)
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(account))
+
+        resp = await client.patch(f"{BASE}/10/toggle")
+        assert resp.status_code == 200
+        # After toggle: is_enabled=True and status reset from ERROR → ACTIVE
+        assert account.is_enabled is True
+        assert account.status == AccountStatus.ACTIVE
+        mock_db.commit.assert_called()
+
+    async def test_toggle_disable(self, client, mock_db):
+        """Toggling an enabled account disables it."""
+        account = _make_account(is_enabled=True, status=AccountStatus.ACTIVE)
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(account))
+
+        resp = await client.patch(f"{BASE}/10/toggle")
+        assert resp.status_code == 200
+        assert account.is_enabled is False
+
+    async def test_toggle_not_found(self, client, mock_db):
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await client.patch(f"{BASE}/999/toggle")
+        assert resp.status_code == 404
+
+
+# ── tests: pull now ─────────────────────────────────────────────────────
+
+
+class TestPullNow:
+    """POST /api/v1/mail-accounts/{account_id}/pull-now"""
+
+    @patch("app.api.v1.endpoints.mail_accounts.process_mail_account_task")
+    async def test_pull_now_success(self, mock_task, client, mock_db):
+        account = _make_account(is_enabled=True)
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(account))
+
+        resp = await client.post(f"{BASE}/10/pull-now")
+        assert resp.status_code == 202
+        assert "queued" in resp.json()["message"].lower()
+        mock_task.delay.assert_called_once_with(10)
+
+    @patch("app.api.v1.endpoints.mail_accounts.process_mail_account_task")
+    async def test_pull_now_disabled_account(self, mock_task, client, mock_db):
+        account = _make_account(is_enabled=False)
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(account))
+
+        resp = await client.post(f"{BASE}/10/pull-now")
+        assert resp.status_code == 409
+        assert "disabled" in resp.json()["detail"].lower()
+        mock_task.delay.assert_not_called()
+
+    @patch("app.api.v1.endpoints.mail_accounts.process_mail_account_task")
+    async def test_pull_now_not_found(self, mock_task, client, mock_db):
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await client.post(f"{BASE}/999/pull-now")
+        assert resp.status_code == 404
+
+
+# ── tests: test connection (new) ────────────────────────────────────────
+
+
+class TestTestConnection:
+    """POST /api/v1/mail-accounts/test"""
+
+    @patch("app.api.v1.endpoints.mail_accounts.MailProcessor")
+    async def test_connection_success(self, mock_processor_cls, client):
+        instance = mock_processor_cls.return_value
+        instance.test_connection = AsyncMock(
+            return_value=(True, "Connection successful")
+        )
+
+        payload = dict(
+            host="pop.example.com",
+            port=995,
+            protocol="pop3_ssl",
+            username="user@example.com",
+            password="pass",
+            use_ssl=True,
+            use_tls=False,
+        )
+        resp = await client.post(f"{BASE}/test", json=payload)
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["success"] is True
+        assert data["message"] == "Connection successful"
+
+    @patch("app.api.v1.endpoints.mail_accounts.MailProcessor")
+    async def test_connection_failure(self, mock_processor_cls, client):
+        instance = mock_processor_cls.return_value
+        instance.test_connection = AsyncMock(return_value=(False, "Connection refused"))
+
+        payload = dict(
+            host="pop.example.com",
+            port=995,
+            protocol="pop3_ssl",
+            username="user@example.com",
+            password="pass",
+            use_ssl=True,
+            use_tls=False,
+        )
+        resp = await client.post(f"{BASE}/test", json=payload)
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["success"] is False
+        assert data["message"] == "Connection refused"
+
+
+# ── tests: test existing connection ─────────────────────────────────────
+
+
+class TestTestExistingConnection:
+    """POST /api/v1/mail-accounts/{account_id}/test"""
+
+    @patch("app.api.v1.endpoints.mail_accounts.MailProcessor")
+    @patch(
+        "app.api.v1.endpoints.mail_accounts.decrypt_credential",
+        return_value="decrypted_pass",
+    )
+    async def test_existing_connection_success(
+        self, mock_decrypt, mock_processor_cls, client, mock_db
+    ):
+        account = _make_account()
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(account))
+
+        instance = mock_processor_cls.return_value
+        instance.test_connection = AsyncMock(return_value=(True, "Connected"))
+
+        resp = await client.post(f"{BASE}/10/test")
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["success"] is True
+        mock_decrypt.assert_called_once_with("encrypted_pass")
+        mock_processor_cls.assert_called_once_with(account, "decrypted_pass")
+
+    async def test_existing_connection_not_found(self, client, mock_db):
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await client.post(f"{BASE}/999/test")
+        assert resp.status_code == 404
+
+    @patch("app.api.v1.endpoints.mail_accounts.MailProcessor")
+    @patch(
+        "app.api.v1.endpoints.mail_accounts.decrypt_credential",
+        side_effect=Exception("Decryption failed"),
+    )
+    async def test_existing_connection_decrypt_failure(
+        self, mock_decrypt, mock_processor_cls, client, mock_db
+    ):
+        account = _make_account()
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(account))
+
+        resp = await client.post(f"{BASE}/10/test")
+        assert resp.status_code == 500
+        assert "decrypt" in resp.json()["detail"].lower()
+
+
+# ── tests: auto-detect ──────────────────────────────────────────────────
+
+
+class TestAutoDetect:
+    """POST /api/v1/mail-accounts/auto-detect"""
+
+    @patch("app.api.v1.endpoints.mail_accounts.MailServerAutoDetect")
+    async def test_auto_detect_success(self, mock_auto_cls, client):
+        mock_auto_cls.detect.return_value = [
+            {"host": "pop.gmail.com", "port": 995, "protocol": "pop3_ssl"}
+        ]
+
+        resp = await client.post(
+            f"{BASE}/auto-detect",
+            json={"email_address": "user@gmail.com"},
+        )
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["success"] is True
+        assert len(data["suggestions"]) == 1
+        mock_auto_cls.detect.assert_called_once_with("user@gmail.com")
+
+    @patch("app.api.v1.endpoints.mail_accounts.MailServerAutoDetect")
+    async def test_auto_detect_no_suggestions(self, mock_auto_cls, client):
+        mock_auto_cls.detect.return_value = []
+
+        resp = await client.post(
+            f"{BASE}/auto-detect",
+            json={"email_address": "user@unknown-domain.xyz"},
+        )
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["success"] is False
+        assert data["suggestions"] == []
+
+
+# ── tests: processing runs ──────────────────────────────────────────────
+
+
+class TestListProcessingRuns:
+    """GET /api/v1/mail-accounts/{account_id}/processing-runs"""
+
+    async def test_list_runs_success(self, client, mock_db):
+        account = _make_account()
+        run = _make_run()
+
+        mock_db.execute = AsyncMock(
+            side_effect=[
+                _scalar_one_or_none(account),  # ownership check
+                _scalar_one(1),  # count
+                _scalars_all([run]),  # run data
+            ]
+        )
+
+        resp = await client.get(f"{BASE}/10/processing-runs")
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["total"] == 1
+        assert data["page"] == 1
+        assert len(data["items"]) == 1
+        assert data["items"][0]["id"] == 100
+        assert data["items"][0]["account_name"] == "Test Account"
+        assert data["items"][0]["account_email"] == "test@example.com"
+
+    async def test_list_runs_account_not_found(self, client, mock_db):
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await client.get(f"{BASE}/999/processing-runs")
+        assert resp.status_code == 404
+
+
+# ── tests: processing logs ──────────────────────────────────────────────
+
+
+class TestListProcessingLogs:
+    """GET /api/v1/mail-accounts/{account_id}/logs"""
+
+    async def test_list_logs_success(self, client, mock_db):
+        account = _make_account()
+        log = _make_log()
+
+        mock_db.execute = AsyncMock(
+            side_effect=[
+                _scalar_one_or_none(account),  # ownership check
+                _scalar_one(1),  # count
+                _scalars_all([log]),  # log data
+            ]
+        )
+
+        resp = await client.get(f"{BASE}/10/logs")
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["total"] == 1
+        assert len(data["items"]) == 1
+        assert data["items"][0]["id"] == 200
+        assert data["items"][0]["level"] == "INFO"
+        assert data["items"][0]["message"] == "Processed email"
+
+    async def test_list_logs_account_not_found(self, client, mock_db):
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await client.get(f"{BASE}/999/logs")
+        assert resp.status_code == 404
diff --git a/backend/tests/unit/test_providers.py b/backend/tests/unit/test_providers.py
new file mode 100644
index 0000000..93563fd
--- /dev/null
+++ b/backend/tests/unit/test_providers.py
@@ -0,0 +1,709 @@
+"""
+Unit tests for provider endpoints (backend/app/api/v1/endpoints/providers.py).
+
+All tests mock the database session, auth dependencies, and external services
+so no real PostgreSQL instance or Google API access is required.
+"""
+
+import pytest
+from datetime import datetime, timezone
+from unittest.mock import AsyncMock, MagicMock, patch
+
+from httpx import AsyncClient, ASGITransport
+
+from app.main import create_application
+from app.core.database import get_db
+from app.core.deps import get_current_active_user
+from app.models.database_models import User, GmailCredential
+from app.services.gmail_service import GmailInjectionError
+
+# ── helpers ──────────────────────────────────────────────────────────────
+
+
+def _make_user(**overrides) -> MagicMock:
+    """Return a MagicMock that behaves like a User ORM instance."""
+    defaults = dict(
+        id=1,
+        email="user@example.com",
+        hashed_password="hashed",
+        full_name="Test User",
+        is_active=True,
+        is_superuser=False,
+        google_id=None,
+        oauth_provider=None,
+        last_login_at=None,
+        created_at=datetime.now(timezone.utc),
+        updated_at=datetime.now(timezone.utc),
+    )
+    defaults.update(overrides)
+    user = MagicMock(spec=User)
+    for k, v in defaults.items():
+        setattr(user, k, v)
+    return user
+
+
+def _make_gmail_credential(**overrides) -> MagicMock:
+    """Return a MagicMock that behaves like a GmailCredential ORM instance."""
+    defaults = dict(
+        id=1,
+        user_id=1,
+        gmail_email="user@gmail.com",
+        encrypted_access_token="encrypted_access",
+        encrypted_refresh_token="encrypted_refresh",
+        token_expiry=datetime.now(timezone.utc),
+        scopes={
+            "granted_scopes": ["scope1"],
+            "import_label_templates": ["imported"],
+        },
+        is_valid=True,
+        last_verified_at=datetime.now(timezone.utc),
+        created_at=datetime.now(timezone.utc),
+        updated_at=datetime.now(timezone.utc),
+        import_label_templates=["imported"],
+        default_import_label_templates=["{{source_email}}", "imported"],
+        granted_scopes=["scope1"],
+    )
+    defaults.update(overrides)
+    cred = MagicMock(spec=GmailCredential)
+    for k, v in defaults.items():
+        setattr(cred, k, v)
+    return cred
+
+
+def _scalar_one_or_none(value):
+    """Create a mock result whose .scalar_one_or_none() returns *value*."""
+    result = MagicMock()
+    result.scalar_one_or_none.return_value = value
+    return result
+
+
+# ── fixtures ─────────────────────────────────────────────────────────────
+
+
+@pytest.fixture
+def app():
+    return create_application()
+
+
+@pytest.fixture
+def test_user():
+    return _make_user()
+
+
+@pytest.fixture
+def mock_db():
+    db = AsyncMock()
+    db.commit = AsyncMock()
+    db.refresh = AsyncMock()
+    db.delete = AsyncMock()
+    db.add = MagicMock()
+    return db
+
+
+@pytest.fixture
+async def auth_client(app, test_user, mock_db):
+    """AsyncClient where the caller is an authenticated active user."""
+
+    async def _override_user():
+        return test_user
+
+    async def _override_db():
+        yield mock_db
+
+    app.dependency_overrides[get_current_active_user] = _override_user
+    app.dependency_overrides[get_db] = _override_db
+
+    transport = ASGITransport(app=app)
+    async with AsyncClient(transport=transport, base_url="http://test") as client:
+        yield client
+
+    app.dependency_overrides.clear()
+
+
+# ═══════════════════════════════════════════════════════════════════════════
+# Provider Presets
+# ═══════════════════════════════════════════════════════════════════════════
+
+
+@pytest.mark.asyncio
+class TestListProviderPresets:
+    async def test_returns_all_presets(self, auth_client):
+        resp = await auth_client.get("/api/v1/providers/presets")
+        assert resp.status_code == 200
+        data = resp.json()
+        assert "providers" in data
+        assert len(data["providers"]) == 13
+        ids = [p["id"] for p in data["providers"]]
+        assert "gmail" in ids
+        assert "outlook" in ids
+        assert "icloud" in ids
+
+
+@pytest.mark.asyncio
+class TestGetProviderPreset:
+    async def test_known_preset(self, auth_client):
+        resp = await auth_client.get("/api/v1/providers/presets/gmail")
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["id"] == "gmail"
+        assert data["name"] == "Gmail"
+        assert "gmail.com" in data["domains"]
+
+    async def test_unknown_preset_404(self, auth_client):
+        resp = await auth_client.get("/api/v1/providers/presets/nonexistent")
+        assert resp.status_code == 404
+        assert "not found" in resp.json()["detail"].lower()
+
+
+# ═══════════════════════════════════════════════════════════════════════════
+# Save Gmail Credential (POST /gmail-credential)
+# ═══════════════════════════════════════════════════════════════════════════
+
+
+@pytest.mark.asyncio
+class TestSaveGmailCredential:
+    @patch("app.api.v1.endpoints.providers.build_gmail_credential_scopes")
+    @patch("app.api.v1.endpoints.providers.encrypt_credential")
+    @patch("app.api.v1.endpoints.providers.GmailService")
+    async def test_create_new_credential(
+        self, mock_gmail_cls, mock_encrypt, mock_build_scopes, auth_client, mock_db
+    ):
+        mock_gmail_instance = MagicMock()
+        mock_gmail_instance.verify_access = AsyncMock(return_value=True)
+        mock_gmail_cls.return_value = mock_gmail_instance
+        mock_encrypt.return_value = "encrypted_token"
+        mock_build_scopes.return_value = {
+            "granted_scopes": [],
+            "import_label_templates": ["{{source_email}}", "imported"],
+        }
+
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        now = datetime.now(timezone.utc)
+
+        async def _populate_on_refresh(obj):
+            """Simulate what the DB does after INSERT + refresh."""
+            obj.id = 1
+            obj.created_at = now
+            obj.updated_at = now
+
+        mock_db.refresh = AsyncMock(side_effect=_populate_on_refresh)
+
+        resp = await auth_client.post(
+            "/api/v1/providers/gmail-credential",
+            json={
+                "access_token": "test_access",
+                "refresh_token": "test_refresh",
+                "gmail_email": "user@gmail.com",
+            },
+        )
+
+        assert resp.status_code == 201
+        data = resp.json()
+        assert data["gmail_email"] == "user@gmail.com"
+        assert data["is_valid"] is True
+
+    @patch("app.api.v1.endpoints.providers.build_gmail_credential_scopes")
+    @patch("app.api.v1.endpoints.providers.encrypt_credential")
+    @patch("app.api.v1.endpoints.providers.GmailService")
+    async def test_update_existing_credential(
+        self, mock_gmail_cls, mock_encrypt, mock_build_scopes, auth_client, mock_db
+    ):
+        mock_gmail_instance = MagicMock()
+        mock_gmail_instance.verify_access = AsyncMock(return_value=True)
+        mock_gmail_cls.return_value = mock_gmail_instance
+        mock_encrypt.return_value = "encrypted_token"
+        mock_build_scopes.return_value = {
+            "granted_scopes": ["scope1"],
+            "import_label_templates": ["imported"],
+        }
+
+        existing = _make_gmail_credential()
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(existing))
+
+        resp = await auth_client.post(
+            "/api/v1/providers/gmail-credential",
+            json={
+                "access_token": "new_access",
+                "refresh_token": "new_refresh",
+                "gmail_email": "user@gmail.com",
+            },
+        )
+
+        assert resp.status_code == 201
+        data = resp.json()
+        assert data["gmail_email"] == "user@gmail.com"
+
+    @patch("app.api.v1.endpoints.providers.GmailService")
+    async def test_invalid_credentials_400(self, mock_gmail_cls, auth_client, mock_db):
+        mock_gmail_instance = MagicMock()
+        mock_gmail_instance.verify_access = AsyncMock(return_value=False)
+        mock_gmail_cls.return_value = mock_gmail_instance
+
+        resp = await auth_client.post(
+            "/api/v1/providers/gmail-credential",
+            json={
+                "access_token": "bad_token",
+                "refresh_token": "bad_refresh",
+                "gmail_email": "user@gmail.com",
+            },
+        )
+
+        assert resp.status_code == 400
+        assert "invalid" in resp.json()["detail"].lower()
+
+
+# ═══════════════════════════════════════════════════════════════════════════
+# Get Gmail Credential (GET /gmail-credential)
+# ═══════════════════════════════════════════════════════════════════════════
+
+
+@pytest.mark.asyncio
+class TestGetGmailCredential:
+    async def test_found(self, auth_client, mock_db):
+        cred = _make_gmail_credential()
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(cred))
+
+        resp = await auth_client.get("/api/v1/providers/gmail-credential")
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["gmail_email"] == "user@gmail.com"
+        assert data["is_valid"] is True
+
+    async def test_not_found_404(self, auth_client, mock_db):
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await auth_client.get("/api/v1/providers/gmail-credential")
+        assert resp.status_code == 404
+
+
+# ═══════════════════════════════════════════════════════════════════════════
+# Delete Gmail Credential (DELETE /gmail-credential)
+# ═══════════════════════════════════════════════════════════════════════════
+
+
+@pytest.mark.asyncio
+class TestDeleteGmailCredential:
+    async def test_delete_success(self, auth_client, mock_db):
+        cred = _make_gmail_credential()
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(cred))
+
+        resp = await auth_client.delete("/api/v1/providers/gmail-credential")
+        assert resp.status_code == 204
+        mock_db.delete.assert_awaited_once_with(cred)
+        mock_db.commit.assert_awaited()
+
+    async def test_delete_not_found_404(self, auth_client, mock_db):
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await auth_client.delete("/api/v1/providers/gmail-credential")
+        assert resp.status_code == 404
+
+
+# ═══════════════════════════════════════════════════════════════════════════
+# Update Import Labels (PUT /gmail-credential/labels)
+# ═══════════════════════════════════════════════════════════════════════════
+
+
+@pytest.mark.asyncio
+class TestUpdateImportLabels:
+    @patch("app.api.v1.endpoints.providers.extract_granted_scopes")
+    @patch("app.api.v1.endpoints.providers.build_gmail_credential_scopes")
+    @patch("app.api.v1.endpoints.providers.normalize_import_label_templates")
+    async def test_update_labels_success(
+        self,
+        mock_normalize,
+        mock_build_scopes,
+        mock_extract_scopes,
+        auth_client,
+        mock_db,
+    ):
+        cred = _make_gmail_credential()
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(cred))
+        mock_normalize.return_value = ["custom-label"]
+        mock_extract_scopes.return_value = ["scope1"]
+        mock_build_scopes.return_value = {
+            "granted_scopes": ["scope1"],
+            "import_label_templates": ["custom-label"],
+        }
+
+        resp = await auth_client.put(
+            "/api/v1/providers/gmail-credential/labels",
+            json={"import_label_templates": ["custom-label"]},
+        )
+
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["gmail_email"] == "user@gmail.com"
+
+    async def test_update_labels_not_found_404(self, auth_client, mock_db):
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await auth_client.put(
+            "/api/v1/providers/gmail-credential/labels",
+            json={"import_label_templates": ["test"]},
+        )
+
+        assert resp.status_code == 404
+
+
+# ═══════════════════════════════════════════════════════════════════════════
+# Get Gmail Authorize URL (GET /gmail/authorize-url)
+# ═══════════════════════════════════════════════════════════════════════════
+
+
+@pytest.mark.asyncio
+class TestGetGmailAuthorizeUrl:
+    @patch("app.api.v1.endpoints.providers.settings")
+    async def test_success(self, mock_settings, auth_client):
+        mock_settings.GOOGLE_CLIENT_ID = "test-client-id"
+
+        resp = await auth_client.get(
+            "/api/v1/providers/gmail/authorize-url",
+            params={"redirect_uri": "http://localhost/callback"},
+        )
+
+        assert resp.status_code == 200
+        data = resp.json()
+        assert "authorization_url" in data
+        assert "test-client-id" in data["authorization_url"]
+        assert "redirect_uri=http" in data["authorization_url"]
+
+    @patch("app.api.v1.endpoints.providers.settings")
+    async def test_google_not_configured_501(self, mock_settings, auth_client):
+        mock_settings.GOOGLE_CLIENT_ID = None
+
+        resp = await auth_client.get(
+            "/api/v1/providers/gmail/authorize-url",
+            params={"redirect_uri": "http://localhost/callback"},
+        )
+
+        assert resp.status_code == 501
+        assert "not configured" in resp.json()["detail"].lower()
+
+
+# ═══════════════════════════════════════════════════════════════════════════
+# Send Debug Email (POST /gmail/debug-email)
+# ═══════════════════════════════════════════════════════════════════════════
+
+
+@pytest.mark.asyncio
+class TestSendDebugEmail:
+    @patch("app.api.v1.endpoints.providers.encrypt_credential")
+    @patch("app.api.v1.endpoints.providers.decrypt_credential")
+    @patch("app.api.v1.endpoints.providers.GmailService")
+    async def test_success(
+        self, mock_gmail_cls, mock_decrypt, mock_encrypt, auth_client, mock_db
+    ):
+        cred = _make_gmail_credential()
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(cred))
+        mock_decrypt.return_value = "decrypted_token"
+
+        mock_gmail_instance = MagicMock()
+        mock_gmail_instance.verify_access = AsyncMock(return_value=True)
+        mock_gmail_instance.inject_debug_email = AsyncMock(
+            return_value={
+                "message_id": "msg1",
+                "thread_id": "t1",
+                "label_ids": ["INBOX"],
+            }
+        )
+        mock_gmail_instance.get_refreshed_token = MagicMock(return_value=None)
+        mock_gmail_cls.return_value = mock_gmail_instance
+
+        resp = await auth_client.post("/api/v1/providers/gmail/debug-email")
+
+        assert resp.status_code == 200
+        data = resp.json()
+        assert data["message_id"] == "msg1"
+        assert data["thread_id"] == "t1"
+        assert "INBOX" in data["label_ids"]
+
+    async def test_no_credentials_400(self, auth_client, mock_db):
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        resp = await auth_client.post("/api/v1/providers/gmail/debug-email")
+
+        assert resp.status_code == 400
+        assert "no valid gmail credentials" in resp.json()["detail"].lower()
+
+    @patch("app.api.v1.endpoints.providers.decrypt_credential")
+    @patch("app.api.v1.endpoints.providers.GmailService")
+    async def test_injection_failure_502(
+        self, mock_gmail_cls, mock_decrypt, auth_client, mock_db
+    ):
+        cred = _make_gmail_credential()
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(cred))
+        mock_decrypt.return_value = "decrypted_token"
+
+        mock_gmail_instance = MagicMock()
+        mock_gmail_instance.inject_debug_email = AsyncMock(
+            side_effect=GmailInjectionError("API error")
+        )
+        mock_gmail_instance.get_refreshed_token = MagicMock(return_value=None)
+        mock_gmail_cls.return_value = mock_gmail_instance
+
+        resp = await auth_client.post("/api/v1/providers/gmail/debug-email")
+
+        assert resp.status_code == 502
+        assert "injection failed" in resp.json()["detail"].lower()
+
+
+# ═══════════════════════════════════════════════════════════════════════════
+# Gmail OAuth Callback (POST /gmail/callback)
+# ═══════════════════════════════════════════════════════════════════════════
+
+
+def _mock_httpx_context_manager(mock_http_client):
+    """Build an httpx.AsyncClient mock that works as an async context manager."""
+    mock_httpx_cls = MagicMock()
+    mock_httpx_cls.return_value.__aenter__ = AsyncMock(return_value=mock_http_client)
+    mock_httpx_cls.return_value.__aexit__ = AsyncMock(return_value=None)
+    return mock_httpx_cls
+
+
+def _make_token_response(status_code=200, json_data=None):
+    """Create a mock httpx response for the token exchange."""
+    resp = MagicMock()
+    resp.status_code = status_code
+    resp.json.return_value = json_data or {
+        "access_token": "new_access_token",
+        "refresh_token": "new_refresh_token",
+        "expires_in": 3600,
+        "scope": "openid email https://www.googleapis.com/auth/gmail.insert",
+    }
+    resp.text = "error" if status_code != 200 else "ok"
+    return resp
+
+
+def _make_profile_response(status_code=200, email="user@gmail.com"):
+    """Create a mock httpx response for the userinfo endpoint."""
+    resp = MagicMock()
+    resp.status_code = status_code
+    resp.json.return_value = {"email": email}
+    return resp
+
+
+@pytest.mark.asyncio
+class TestGmailCallback:
+    @patch("app.api.v1.endpoints.providers.build_gmail_credential_scopes")
+    @patch("app.api.v1.endpoints.providers.encrypt_credential")
+    @patch("app.api.v1.endpoints.providers.GmailService")
+    @patch("app.api.v1.endpoints.providers.httpx.AsyncClient")
+    @patch("app.api.v1.endpoints.providers.settings")
+    async def test_new_credential_success(
+        self,
+        mock_settings,
+        mock_httpx_cls,
+        mock_gmail_cls,
+        mock_encrypt,
+        mock_build_scopes,
+        auth_client,
+        mock_db,
+    ):
+        mock_settings.GOOGLE_CLIENT_ID = "client-id"
+        mock_settings.GOOGLE_CLIENT_SECRET = "client-secret"
+
+        mock_http_client = AsyncMock()
+        token_resp = _make_token_response()
+        profile_resp = _make_profile_response()
+        mock_http_client.post = AsyncMock(return_value=token_resp)
+        mock_http_client.get = AsyncMock(return_value=profile_resp)
+        mock_httpx_cls.return_value.__aenter__ = AsyncMock(
+            return_value=mock_http_client
+        )
+        mock_httpx_cls.return_value.__aexit__ = AsyncMock(return_value=None)
+
+        mock_gmail_instance = MagicMock()
+        mock_gmail_instance.verify_access = AsyncMock(return_value=True)
+        mock_gmail_cls.return_value = mock_gmail_instance
+
+        mock_encrypt.return_value = "encrypted"
+        mock_build_scopes.return_value = {
+            "granted_scopes": ["openid", "email"],
+            "import_label_templates": ["{{source_email}}", "imported"],
+        }
+
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(None))
+
+        now = datetime.now(timezone.utc)
+
+        async def _populate_on_refresh(obj):
+            """Simulate what the DB does after INSERT + refresh."""
+            obj.id = 1
+            obj.created_at = now
+            obj.updated_at = now
+
+        mock_db.refresh = AsyncMock(side_effect=_populate_on_refresh)
+
+        resp = await auth_client.post(
+            "/api/v1/providers/gmail/callback",
+            json={
+                "code": "auth_code",
+                "redirect_uri": "http://localhost/callback",
+            },
+        )
+
+        assert resp.status_code == 201
+        data = resp.json()
+        assert data["gmail_email"] == "user@gmail.com"
+        assert data["is_valid"] is True
+
+    @patch("app.api.v1.endpoints.providers.build_gmail_credential_scopes")
+    @patch("app.api.v1.endpoints.providers.encrypt_credential")
+    @patch("app.api.v1.endpoints.providers.GmailService")
+    @patch("app.api.v1.endpoints.providers.httpx.AsyncClient")
+    @patch("app.api.v1.endpoints.providers.settings")
+    async def test_update_existing_credential(
+        self,
+        mock_settings,
+        mock_httpx_cls,
+        mock_gmail_cls,
+        mock_encrypt,
+        mock_build_scopes,
+        auth_client,
+        mock_db,
+    ):
+        mock_settings.GOOGLE_CLIENT_ID = "client-id"
+        mock_settings.GOOGLE_CLIENT_SECRET = "client-secret"
+
+        mock_http_client = AsyncMock()
+        token_resp = _make_token_response()
+        profile_resp = _make_profile_response()
+        mock_http_client.post = AsyncMock(return_value=token_resp)
+        mock_http_client.get = AsyncMock(return_value=profile_resp)
+        mock_httpx_cls.return_value.__aenter__ = AsyncMock(
+            return_value=mock_http_client
+        )
+        mock_httpx_cls.return_value.__aexit__ = AsyncMock(return_value=None)
+
+        mock_gmail_instance = MagicMock()
+        mock_gmail_instance.verify_access = AsyncMock(return_value=True)
+        mock_gmail_cls.return_value = mock_gmail_instance
+
+        mock_encrypt.return_value = "encrypted"
+        mock_build_scopes.return_value = {
+            "granted_scopes": ["openid"],
+            "import_label_templates": ["imported"],
+        }
+
+        existing = _make_gmail_credential()
+        mock_db.execute = AsyncMock(return_value=_scalar_one_or_none(existing))
+
+        resp = await auth_client.post(
+            "/api/v1/providers/gmail/callback",
+            json={
+                "code": "auth_code",
+                "redirect_uri": "http://localhost/callback",
+            },
+        )
+
+        assert resp.status_code == 201
+        data = resp.json()
+        assert data["gmail_email"] == "user@gmail.com"
+
+    @patch("app.api.v1.endpoints.providers.settings")
+    async def test_google_not_configured_501(self, mock_settings, auth_client):
+        mock_settings.GOOGLE_CLIENT_ID = None
+        mock_settings.GOOGLE_CLIENT_SECRET = None
+
+        resp = await auth_client.post(
+            "/api/v1/providers/gmail/callback",
+            json={
+                "code": "auth_code",
+                "redirect_uri": "http://localhost/callback",
+            },
+        )
+
+        assert resp.status_code == 501
+        assert "not configured" in resp.json()["detail"].lower()
+
+    @patch("app.api.v1.endpoints.providers.httpx.AsyncClient")
+    @patch("app.api.v1.endpoints.providers.settings")
+    async def test_token_exchange_fails_400(
+        self, mock_settings, mock_httpx_cls, auth_client
+    ):
+        mock_settings.GOOGLE_CLIENT_ID = "client-id"
+        mock_settings.GOOGLE_CLIENT_SECRET = "client-secret"
+
+        mock_http_client = AsyncMock()
+        mock_http_client.post = AsyncMock(
+            return_value=_make_token_response(status_code=400, json_data={})
+        )
+        mock_httpx_cls.return_value.__aenter__ = AsyncMock(
+            return_value=mock_http_client
+        )
+        mock_httpx_cls.return_value.__aexit__ = AsyncMock(return_value=None)
+
+        resp = await auth_client.post(
+            "/api/v1/providers/gmail/callback",
+            json={
+                "code": "bad_code",
+                "redirect_uri": "http://localhost/callback",
+            },
+        )
+
+        assert resp.status_code == 400
+        assert "exchange" in resp.json()["detail"].lower()
+
+    @patch("app.api.v1.endpoints.providers.httpx.AsyncClient")
+    @patch("app.api.v1.endpoints.providers.settings")
+    async def test_no_access_token_returned_400(
+        self, mock_settings, mock_httpx_cls, auth_client
+    ):
+        mock_settings.GOOGLE_CLIENT_ID = "client-id"
+        mock_settings.GOOGLE_CLIENT_SECRET = "client-secret"
+
+        mock_http_client = AsyncMock()
+        # Token response OK but missing access_token
+        token_resp = _make_token_response(
+            json_data={"refresh_token": "rt", "expires_in": 3600}
+        )
+        mock_http_client.post = AsyncMock(return_value=token_resp)
+        mock_httpx_cls.return_value.__aenter__ = AsyncMock(
+            return_value=mock_http_client
+        )
+        mock_httpx_cls.return_value.__aexit__ = AsyncMock(return_value=None)
+
+        resp = await auth_client.post(
+            "/api/v1/providers/gmail/callback",
+            json={
+                "code": "auth_code",
+                "redirect_uri": "http://localhost/callback",
+            },
+        )
+
+        assert resp.status_code == 400
+        assert "access token" in resp.json()["detail"].lower()
+
+    @patch("app.api.v1.endpoints.providers.GmailService")
+    @patch("app.api.v1.endpoints.providers.httpx.AsyncClient")
+    @patch("app.api.v1.endpoints.providers.settings")
+    async def test_verification_fails_400(
+        self, mock_settings, mock_httpx_cls, mock_gmail_cls, auth_client
+    ):
+        mock_settings.GOOGLE_CLIENT_ID = "client-id"
+        mock_settings.GOOGLE_CLIENT_SECRET = "client-secret"
+
+        mock_http_client = AsyncMock()
+        mock_http_client.post = AsyncMock(return_value=_make_token_response())
+        mock_http_client.get = AsyncMock(return_value=_make_profile_response())
+        mock_httpx_cls.return_value.__aenter__ = AsyncMock(
+            return_value=mock_http_client
+        )
+        mock_httpx_cls.return_value.__aexit__ = AsyncMock(return_value=None)
+
+        mock_gmail_instance = MagicMock()
+        mock_gmail_instance.verify_access = AsyncMock(return_value=False)
+        mock_gmail_cls.return_value = mock_gmail_instance
+
+        resp = await auth_client.post(
+            "/api/v1/providers/gmail/callback",
+            json={
+                "code": "auth_code",
+                "redirect_uri": "http://localhost/callback",
+            },
+        )
+
+        assert resp.status_code == 400
+        assert "verify" in resp.json()["detail"].lower()
diff --git a/docs/TODO.md b/docs/TODO.md
index fe1600b..bb89f42 100644
--- a/docs/TODO.md
+++ b/docs/TODO.md
@@ -122,9 +122,14 @@ Comprehensive task breakdown for repository improvements and production readines
 - [x] Write tests for Celery tasks (96% coverage for `tasks.py`)
 - [x] Write unit tests for admin endpoints (87 tests, 100% coverage on admin.py)
 - [x] **Frontend test coverage**: Added 113 new tests across 7 new test suites covering all components and utility functions. Installed `@testing-library/react`, `@testing-library/jest-dom`, `@testing-library/user-event`. New suites: `date-utils` (30 tests), API interceptors (9 tests), `AuthGuard` (6 tests), `QueryProvider` (2 tests), `DashboardLayout` (14 tests), `NotificationWizard` (32 tests), `ProviderWizard` (20 tests). Total frontend: 119 tests across 8 suites.
+- [x] **AddMailAccountModal test coverage**: 28 tests covering create/edit mode rendering, provider wizard flow, form fields, auto-detect, test connection, submit mutations, error extraction, and modal interactions. Total frontend: 147 tests across 9 suites.
+- [x] **Expanded `api.ts` test coverage**: Added 56 new tests covering all 10 API objects (`authApi`, `userApi`, `mailAccountsApi`, `processingRunsApi`, `gmailApi`, `smtpApi`, `adminApi`, `notificationsApi`, `adminNotificationsApi`, `versionApi`). Every exported method now has at least one test verifying correct HTTP method, URL, parameters, and return value. Total: 65 tests in `api.test.ts`.
 
 ### In Progress 🔨
-- [ ] Write unit tests for authentication (target 80%+ coverage)
+- [x] Write unit tests for authentication (22 tests covering register, login, Google OAuth, authorize-url, and helper functions)
+- [x] Write unit tests for mail account endpoints (30 tests covering CRUD, toggle, pull-now, test connection, auto-detect, processing runs/logs)
+- [x] Write unit tests for provider endpoints (23 tests covering presets, Gmail credential CRUD, import labels, authorize URL, debug email, OAuth callback)
+- [x] **Expanded `gmail_service.py` test coverage**: 10 new tests covering `inject_email` HttpError branch, `get_or_create_label` (existing/create/HttpError/generic-error), `inject_debug_email` full flow, `get_refreshed_token` (changed/unchanged), and `service` property lazy initialization — 24 total tests in `test_gmail_service.py`
 - [ ] Write unit tests for mail processing
 - [ ] Write integration tests for API endpoints
 
diff --git a/frontend/src/components/AddMailAccountModal.test.tsx b/frontend/src/components/AddMailAccountModal.test.tsx
new file mode 100644
index 0000000..8b6ad1e
--- /dev/null
+++ b/frontend/src/components/AddMailAccountModal.test.tsx
@@ -0,0 +1,546 @@
+import React from 'react';
+import { render, screen, fireEvent, waitFor } from '@testing-library/react';
+import { AddMailAccountModal } from './AddMailAccountModal';
+import { MailAccount } from '@/lib/api';
+
+// ── Mock state ──────────────────────────────────────────────────────────────
+const mockMutateAsyncCreate = jest.fn().mockResolvedValue({});
+const mockMutateAsyncUpdate = jest.fn().mockResolvedValue({});
+const mockInvalidateQueries = jest.fn();
+
+let createIsPending = false;
+let updateIsPending = false;
+let mutationCallCount = 0;
+
+// ── Mocks ───────────────────────────────────────────────────────────────────
+
+jest.mock('@tanstack/react-query', () => ({
+  useMutation: jest.fn().mockImplementation(() => {
+    mutationCallCount++;
+    if (mutationCallCount % 2 === 1) {
+      return { mutateAsync: mockMutateAsyncCreate, isPending: createIsPending };
+    }
+    return { mutateAsync: mockMutateAsyncUpdate, isPending: updateIsPending };
+  }),
+  useQueryClient: () => ({
+    invalidateQueries: mockInvalidateQueries,
+  }),
+}));
+
+jest.mock('@/lib/api', () => ({
+  mailAccountsApi: {
+    create: jest.fn(),
+    update: jest.fn(),
+    test: jest.fn(),
+    testExisting: jest.fn(),
+    autoDetect: jest.fn(),
+  },
+}));
+
+jest.mock('@/store/authStore', () => ({
+  useAuthStore: () => ({
+    user: { email: 'currentuser@example.com' },
+  }),
+}));
+
+jest.mock('lucide-react', () => ({
+  X: ({ className }: { className?: string }) => (
+    <span data-testid="icon-X" className={className} />
+  ),
+  Loader2: ({ className }: { className?: string }) => (
+    <span data-testid="icon-Loader2" className={className} />
+  ),
+  CheckCircle: ({ className }: { className?: string }) => (
+    <span data-testid="icon-CheckCircle" className={className} />
+  ),
+  XCircle: ({ className }: { className?: string }) => (
+    <span data-testid="icon-XCircle" className={className} />
+  ),
+}));
+
+jest.mock('./ProviderWizard', () => ({
+  ProviderWizard: ({
+    onSelect,
+    onManual,
+  }: {
+    onSelect: (config: unknown) => void;
+    onManual: () => void;
+  }) => (
+    <div data-testid="provider-wizard">
+      <button
+        onClick={() =>
+          onSelect({
+            name: 'Gmail',
+            provider_name: 'Gmail',
+            protocol: 'imap_ssl',
+            host: 'imap.gmail.com',
+            port: 993,
+            use_ssl: true,
+          })
+        }
+      >
+        Select Gmail
+      </button>
+      <button onClick={onManual}>Manual Setup</button>
+    </div>
+  ),
+}));
+
+// ── Helpers ──────────────────────────────────────────────────────────────────
+
+const mockAccount: MailAccount = {
+  id: 42,
+  user_id: 1,
+  name: 'My Work Email',
+  email_address: 'work@example.com',
+  protocol: 'imap_ssl',
+  host: 'imap.example.com',
+  port: 993,
+  use_ssl: true,
+  use_tls: false,
+  username: 'work@example.com',
+  forward_to: 'me@gmail.com',
+  delivery_method: 'gmail_api',
+  is_enabled: true,
+  check_interval_minutes: 10,
+  max_emails_per_check: 25,
+  delete_after_forward: false,
+  status: 'active',
+  provider_name: 'Gmail',
+  auto_detected: false,
+  total_emails_processed: 100,
+  created_at: '2024-01-01T00:00:00Z',
+  updated_at: '2024-01-02T00:00:00Z',
+  last_checked_at: '2024-01-02T12:00:00Z',
+  last_error: null,
+};
+
+const { mailAccountsApi } = jest.requireMock('@/lib/api') as {
+  mailAccountsApi: {
+    create: jest.Mock;
+    update: jest.Mock;
+    test: jest.Mock;
+    testExisting: jest.Mock;
+    autoDetect: jest.Mock;
+  };
+};
+
+// ── Setup / Teardown ────────────────────────────────────────────────────────
+
+beforeEach(() => {
+  jest.clearAllMocks();
+  mutationCallCount = 0;
+  createIsPending = false;
+  updateIsPending = false;
+});
+
+// ── Tests ───────────────────────────────────────────────────────────────────
+
+describe('AddMailAccountModal', () => {
+  // 1. Create mode renders ProviderWizard
+  it('renders ProviderWizard in create mode', () => {
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    expect(screen.getByTestId('provider-wizard')).toBeInTheDocument();
+  });
+
+  // 2. Edit mode shows form with pre-filled data
+  it('renders form with pre-filled data in edit mode', () => {
+    render(<AddMailAccountModal account={mockAccount} onClose={jest.fn()} />);
+    expect(screen.queryByTestId('provider-wizard')).not.toBeInTheDocument();
+    expect(screen.getByDisplayValue('My Work Email')).toBeInTheDocument();
+    expect(screen.getByDisplayValue('work@example.com')).toBeInTheDocument();
+    expect(screen.getByDisplayValue('imap.example.com')).toBeInTheDocument();
+    expect(screen.getByDisplayValue('993')).toBeInTheDocument();
+  });
+
+  // 3. Shows correct title for create mode
+  it('shows "Add Mail Account" title in create mode', () => {
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    expect(screen.getByText('Add Mail Account')).toBeInTheDocument();
+  });
+
+  // 4. Shows correct title for edit mode
+  it('shows "Edit Mail Account" title in edit mode', () => {
+    render(<AddMailAccountModal account={mockAccount} onClose={jest.fn()} />);
+    expect(screen.getByText('Edit Mail Account')).toBeInTheDocument();
+  });
+
+  // 5. Provider selection fills form and advances to form step
+  it('fills form and advances to form step on provider selection', () => {
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Select Gmail'));
+    // Wizard should be gone, form should be visible
+    expect(screen.queryByTestId('provider-wizard')).not.toBeInTheDocument();
+    expect(screen.getByDisplayValue('Gmail')).toBeInTheDocument();
+    expect(screen.getByDisplayValue('imap.gmail.com')).toBeInTheDocument();
+    expect(screen.getByDisplayValue('993')).toBeInTheDocument();
+  });
+
+  // 6. Back to provider selection works in create mode
+  it('goes back to provider selection in create mode', () => {
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    // Advance to form via manual
+    fireEvent.click(screen.getByText('Manual Setup'));
+    expect(screen.queryByTestId('provider-wizard')).not.toBeInTheDocument();
+    // Click back
+    fireEvent.click(screen.getByText('← Back to provider selection'));
+    expect(screen.getByTestId('provider-wizard')).toBeInTheDocument();
+  });
+
+  // 7. No back button in edit mode
+  it('does not show back button in edit mode', () => {
+    render(<AddMailAccountModal account={mockAccount} onClose={jest.fn()} />);
+    expect(screen.queryByText('← Back to provider selection')).not.toBeInTheDocument();
+  });
+
+  // 8. Form field changes update state
+  it('updates form state when fields change', () => {
+    render(<AddMailAccountModal account={mockAccount} onClose={jest.fn()} />);
+    const nameInput = screen.getByDisplayValue('My Work Email');
+    fireEvent.change(nameInput, { target: { name: 'name', value: 'New Name', type: 'text' } });
+    expect(screen.getByDisplayValue('New Name')).toBeInTheDocument();
+  });
+
+  // 9. Username/email sync
+  it('syncs email_address with username when username changes', () => {
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Manual Setup'));
+    const usernameInput = screen.getByPlaceholderText('user@example.com');
+    fireEvent.change(usernameInput, {
+      target: { name: 'username', value: 'new@example.com', type: 'text' },
+    });
+    // The forward_to field is a different input; email_address is internal state
+    // We can verify by checking the username input value
+    expect(usernameInput).toHaveValue('new@example.com');
+  });
+
+  // 10. Checkbox changes work
+  it('toggles checkbox values', () => {
+    render(<AddMailAccountModal account={mockAccount} onClose={jest.fn()} />);
+    const sslCheckbox = screen.getByLabelText('Use SSL/TLS');
+    expect(sslCheckbox).toBeChecked();
+    fireEvent.click(sslCheckbox);
+    expect(sslCheckbox).not.toBeChecked();
+
+    const deleteCheckbox = screen.getByLabelText('Delete after forwarding');
+    expect(deleteCheckbox).not.toBeChecked();
+    fireEvent.click(deleteCheckbox);
+    expect(deleteCheckbox).toBeChecked();
+
+    const enabledCheckbox = screen.getByLabelText('Enabled');
+    expect(enabledCheckbox).toBeChecked();
+    fireEvent.click(enabledCheckbox);
+    expect(enabledCheckbox).not.toBeChecked();
+  });
+
+  // 11. Auto-detect success updates form fields
+  it('updates form on successful auto-detect', async () => {
+    mailAccountsApi.autoDetect.mockResolvedValue({
+      success: true,
+      suggestions: [{ protocol: 'pop3_ssl', host: 'pop.detected.com', port: 995, use_ssl: true }],
+    });
+    jest.spyOn(window, 'alert').mockImplementation(() => {});
+
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Manual Setup'));
+    const usernameInput = screen.getByPlaceholderText('user@example.com');
+    fireEvent.change(usernameInput, {
+      target: { name: 'username', value: 'test@detect.com', type: 'text' },
+    });
+    fireEvent.click(screen.getByText('Auto-Detect'));
+
+    await waitFor(() => {
+      expect(screen.getByDisplayValue('pop.detected.com')).toBeInTheDocument();
+    });
+    expect(window.alert).toHaveBeenCalledWith('Settings auto-detected successfully!');
+  });
+
+  // 12. Auto-detect failure shows alert
+  it('shows alert on auto-detect failure', async () => {
+    mailAccountsApi.autoDetect.mockRejectedValue(new Error('fail'));
+    jest.spyOn(window, 'alert').mockImplementation(() => {});
+
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Manual Setup'));
+    const usernameInput = screen.getByPlaceholderText('user@example.com');
+    fireEvent.change(usernameInput, {
+      target: { name: 'username', value: 'test@fail.com', type: 'text' },
+    });
+    fireEvent.click(screen.getByText('Auto-Detect'));
+
+    await waitFor(() => {
+      expect(window.alert).toHaveBeenCalledWith(
+        'Failed to auto-detect settings. Please enter manually.'
+      );
+    });
+  });
+
+  // 13. Auto-detect requires username
+  it('alerts when auto-detect is attempted without username', () => {
+    jest.spyOn(window, 'alert').mockImplementation(() => {});
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Manual Setup'));
+    fireEvent.click(screen.getByText('Auto-Detect'));
+    expect(window.alert).toHaveBeenCalledWith('Please enter an email address first');
+  });
+
+  // 14. Test connection success
+  it('shows success message on successful test connection', async () => {
+    mailAccountsApi.test.mockResolvedValue({ success: true, message: 'Connected!' });
+
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Manual Setup'));
+
+    // Fill required fields
+    const usernameInput = screen.getByPlaceholderText('user@example.com');
+    const passwordInput = screen.getByPlaceholderText('Password');
+    const hostInput = screen.getByPlaceholderText('pop.gmail.com');
+
+    fireEvent.change(usernameInput, {
+      target: { name: 'username', value: 'u@test.com', type: 'text' },
+    });
+    fireEvent.change(passwordInput, {
+      target: { name: 'password', value: 'pass123', type: 'password' },
+    });
+    fireEvent.change(hostInput, {
+      target: { name: 'host', value: 'mail.test.com', type: 'text' },
+    });
+
+    fireEvent.click(screen.getByText('Test Connection'));
+
+    await waitFor(() => {
+      expect(screen.getByText('Connected!')).toBeInTheDocument();
+    });
+    expect(screen.getByTestId('icon-CheckCircle')).toBeInTheDocument();
+  });
+
+  // 15. Test connection error
+  it('shows error message on failed test connection', async () => {
+    mailAccountsApi.test.mockResolvedValue({ success: false, message: 'Auth failed' });
+
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Manual Setup'));
+
+    const usernameInput = screen.getByPlaceholderText('user@example.com');
+    const passwordInput = screen.getByPlaceholderText('Password');
+    const hostInput = screen.getByPlaceholderText('pop.gmail.com');
+
+    fireEvent.change(usernameInput, {
+      target: { name: 'username', value: 'u@test.com', type: 'text' },
+    });
+    fireEvent.change(passwordInput, {
+      target: { name: 'password', value: 'wrong', type: 'password' },
+    });
+    fireEvent.change(hostInput, {
+      target: { name: 'host', value: 'mail.test.com', type: 'text' },
+    });
+
+    fireEvent.click(screen.getByText('Test Connection'));
+
+    await waitFor(() => {
+      expect(screen.getByText('Auth failed')).toBeInTheDocument();
+    });
+    expect(screen.getByTestId('icon-XCircle')).toBeInTheDocument();
+  });
+
+  // 16. Test connection missing fields
+  it('shows validation error when test fields are missing', async () => {
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Manual Setup'));
+    fireEvent.click(screen.getByText('Test Connection'));
+
+    await waitFor(() => {
+      expect(
+        screen.getByText('Please fill in username, password, and host')
+      ).toBeInTheDocument();
+    });
+  });
+
+  // 17. Test connection in edit mode uses testExisting when no password
+  it('uses testExisting in edit mode when no password is entered', async () => {
+    mailAccountsApi.testExisting.mockResolvedValue({
+      success: true,
+      message: 'Existing OK',
+    });
+
+    render(<AddMailAccountModal account={mockAccount} onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Test Connection'));
+
+    await waitFor(() => {
+      expect(mailAccountsApi.testExisting).toHaveBeenCalledWith(42);
+    });
+    expect(screen.getByText('Existing OK')).toBeInTheDocument();
+  });
+
+  // 18. Submit in create mode calls createMutation
+  it('calls create mutation on submit in create mode', async () => {
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Manual Setup'));
+
+    // Fill required form fields
+    const nameInput = screen.getByPlaceholderText('My Email Account');
+    const usernameInput = screen.getByPlaceholderText('user@example.com');
+    const passwordInput = screen.getByPlaceholderText('Password');
+    const hostInput = screen.getByPlaceholderText('pop.gmail.com');
+    const forwardInput = screen.getByPlaceholderText('you@gmail.com');
+
+    fireEvent.change(nameInput, {
+      target: { name: 'name', value: 'Test Account', type: 'text' },
+    });
+    fireEvent.change(usernameInput, {
+      target: { name: 'username', value: 'user@test.com', type: 'text' },
+    });
+    fireEvent.change(passwordInput, {
+      target: { name: 'password', value: 'secret', type: 'password' },
+    });
+    fireEvent.change(hostInput, {
+      target: { name: 'host', value: 'pop.test.com', type: 'text' },
+    });
+    fireEvent.change(forwardInput, {
+      target: { name: 'forward_to', value: 'fwd@gmail.com', type: 'email' },
+    });
+
+    fireEvent.click(screen.getByText('Save'));
+
+    await waitFor(() => {
+      expect(mockMutateAsyncCreate).toHaveBeenCalled();
+    });
+  });
+
+  // 19. Submit in edit mode calls updateMutation (omits password when blank)
+  it('calls update mutation on submit in edit mode, omitting blank password', async () => {
+    render(<AddMailAccountModal account={mockAccount} onClose={jest.fn()} />);
+
+    fireEvent.click(screen.getByText('Save'));
+
+    await waitFor(() => {
+      expect(mockMutateAsyncUpdate).toHaveBeenCalled();
+    });
+    const updateArg = mockMutateAsyncUpdate.mock.calls[0][0];
+    expect(updateArg.password).toBeUndefined();
+    expect(updateArg.name).toBe('My Work Email');
+  });
+
+  // 20. Close button calls onClose
+  it('calls onClose when close (X) button is clicked', () => {
+    const onClose = jest.fn();
+    render(<AddMailAccountModal account={mockAccount} onClose={onClose} />);
+    // The X icon button is the one containing the X icon
+    const closeButton = screen.getByTestId('icon-X').closest('button')!;
+    fireEvent.click(closeButton);
+    expect(onClose).toHaveBeenCalled();
+  });
+
+  // 21. Backdrop click calls onClose
+  it('calls onClose when backdrop is clicked', () => {
+    const onClose = jest.fn();
+    const { container } = render(
+      <AddMailAccountModal account={mockAccount} onClose={onClose} />
+    );
+    // Backdrop is the div with bg-gray-500/75
+    const backdrop = container.querySelector('.bg-gray-500\\/75');
+    expect(backdrop).toBeTruthy();
+    fireEvent.click(backdrop!);
+    expect(onClose).toHaveBeenCalled();
+  });
+
+  // 22. Cancel button calls onClose
+  it('calls onClose when Cancel button is clicked', () => {
+    const onClose = jest.fn();
+    render(<AddMailAccountModal account={mockAccount} onClose={onClose} />);
+    fireEvent.click(screen.getByText('Cancel'));
+    expect(onClose).toHaveBeenCalled();
+  });
+
+  // 23. Save button shows "Saving..." when mutation is pending
+  it('shows "Saving..." when create mutation is pending', () => {
+    createIsPending = true;
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Manual Setup'));
+    expect(screen.getByText('Saving...')).toBeInTheDocument();
+  });
+
+  it('shows "Saving..." when update mutation is pending', () => {
+    updateIsPending = true;
+    render(<AddMailAccountModal account={mockAccount} onClose={jest.fn()} />);
+    expect(screen.getByText('Saving...')).toBeInTheDocument();
+  });
+
+  // 24. Error message extraction - string detail
+  it('shows string error detail on submit failure', async () => {
+    jest.spyOn(window, 'alert').mockImplementation(() => {});
+    mockMutateAsyncUpdate.mockRejectedValueOnce({
+      response: { data: { detail: 'Account already exists' } },
+    });
+
+    render(<AddMailAccountModal account={mockAccount} onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Save'));
+
+    await waitFor(() => {
+      expect(window.alert).toHaveBeenCalledWith('Account already exists');
+    });
+  });
+
+  // 25. Error message extraction - array detail (validation errors)
+  it('shows joined validation errors on submit failure', async () => {
+    jest.spyOn(window, 'alert').mockImplementation(() => {});
+    mockMutateAsyncUpdate.mockRejectedValueOnce({
+      response: {
+        data: {
+          detail: [{ msg: 'field required' }, { msg: 'invalid email' }],
+        },
+      },
+    });
+
+    render(<AddMailAccountModal account={mockAccount} onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Save'));
+
+    await waitFor(() => {
+      expect(window.alert).toHaveBeenCalledWith('field required; invalid email');
+    });
+  });
+
+  // 26. Error message extraction - Error instance
+  it('shows Error.message on submit failure with Error instance', async () => {
+    jest.spyOn(window, 'alert').mockImplementation(() => {});
+    mockMutateAsyncCreate.mockRejectedValueOnce(new Error('Network error'));
+
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Manual Setup'));
+    fireEvent.click(screen.getByText('Save'));
+
+    await waitFor(() => {
+      expect(window.alert).toHaveBeenCalledWith('Network error');
+    });
+  });
+
+  // Test connection error extraction
+  it('shows extracted error message on test connection exception', async () => {
+    mailAccountsApi.test.mockRejectedValue({
+      response: { data: { detail: 'Timeout' } },
+    });
+
+    render(<AddMailAccountModal onClose={jest.fn()} />);
+    fireEvent.click(screen.getByText('Manual Setup'));
+
+    const usernameInput = screen.getByPlaceholderText('user@example.com');
+    const passwordInput = screen.getByPlaceholderText('Password');
+    const hostInput = screen.getByPlaceholderText('pop.gmail.com');
+
+    fireEvent.change(usernameInput, {
+      target: { name: 'username', value: 'u@t.com', type: 'text' },
+    });
+    fireEvent.change(passwordInput, {
+      target: { name: 'password', value: 'p', type: 'password' },
+    });
+    fireEvent.change(hostInput, {
+      target: { name: 'host', value: 'h.com', type: 'text' },
+    });
+
+    fireEvent.click(screen.getByText('Test Connection'));
+
+    await waitFor(() => {
+      expect(screen.getByText('Timeout')).toBeInTheDocument();
+    });
+  });
+});
diff --git a/frontend/src/lib/api.test.ts b/frontend/src/lib/api.test.ts
index 5c51f3e..7fd9474 100644
--- a/frontend/src/lib/api.test.ts
+++ b/frontend/src/lib/api.test.ts
@@ -126,3 +126,736 @@ describe('Response interceptor', () => {
     await expect(responseErrorInterceptor!(error)).rejects.toBe(error);
   });
 });
+
+// ── API Object Tests ────────────────────────────────────────────────────
+
+/* eslint-disable @typescript-eslint/no-require-imports */
+const {
+  authApi,
+  userApi,
+  mailAccountsApi,
+  processingRunsApi,
+  gmailApi,
+  smtpApi,
+  adminApi,
+  notificationsApi,
+  adminNotificationsApi,
+  versionApi,
+} = require('./api');
+
+// ── authApi ─────────────────────────────────────────────────────────────
+
+describe('authApi', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('login should post form data to /auth/login', async () => {
+    const tokenData = { access_token: 'tok', refresh_token: 'ref', token_type: 'bearer' };
+    mockAxiosInstance.post.mockResolvedValue({ data: tokenData });
+
+    const result = await authApi.login({ username: 'u@test.com', password: 'pw' });
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith(
+      '/auth/login',
+      expect.any(URLSearchParams),
+      expect.objectContaining({
+        headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
+      })
+    );
+    const formData: URLSearchParams = mockAxiosInstance.post.mock.calls[0][1];
+    expect(formData.get('username')).toBe('u@test.com');
+    expect(formData.get('password')).toBe('pw');
+    expect(result).toEqual(tokenData);
+  });
+
+  it('register should post user data to /auth/register', async () => {
+    const user = { id: 1, email: 'u@test.com', full_name: 'Test' };
+    mockAxiosInstance.post.mockResolvedValue({ data: user });
+
+    const result = await authApi.register({ email: 'u@test.com', password: 'pw', full_name: 'Test' });
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/auth/register', {
+      email: 'u@test.com',
+      password: 'pw',
+      full_name: 'Test',
+    });
+    expect(result).toEqual(user);
+  });
+
+  it('googleAuth should post code and redirect_uri to /auth/google', async () => {
+    const tokenData = { access_token: 'tok', refresh_token: 'ref', token_type: 'bearer' };
+    mockAxiosInstance.post.mockResolvedValue({ data: tokenData });
+
+    const result = await authApi.googleAuth('code123', 'http://redirect');
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/auth/google', {
+      code: 'code123',
+      redirect_uri: 'http://redirect',
+    });
+    expect(result).toEqual(tokenData);
+  });
+
+  it('getGoogleAuthUrl should get authorization URL with redirect_uri param', async () => {
+    mockAxiosInstance.get.mockResolvedValue({
+      data: { authorization_url: 'https://google.com/auth' },
+    });
+
+    const result = await authApi.getGoogleAuthUrl('http://redirect');
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/auth/google/authorize-url', {
+      params: { redirect_uri: 'http://redirect' },
+    });
+    expect(result).toBe('https://google.com/auth');
+  });
+});
+
+// ── userApi ─────────────────────────────────────────────────────────────
+
+describe('userApi', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('getCurrentUser should get /users/me', async () => {
+    const user = { id: 1, email: 'u@test.com' };
+    mockAxiosInstance.get.mockResolvedValue({ data: user });
+
+    const result = await userApi.getCurrentUser();
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/users/me');
+    expect(result).toEqual(user);
+  });
+
+  it('updateProfile should put data to /users/me', async () => {
+    const user = { id: 1, email: 'new@test.com', full_name: 'New' };
+    mockAxiosInstance.put.mockResolvedValue({ data: user });
+
+    const result = await userApi.updateProfile({ full_name: 'New', email: 'new@test.com' });
+
+    expect(mockAxiosInstance.put).toHaveBeenCalledWith('/users/me', {
+      full_name: 'New',
+      email: 'new@test.com',
+    });
+    expect(result).toEqual(user);
+  });
+});
+
+// ── mailAccountsApi ─────────────────────────────────────────────────────
+
+describe('mailAccountsApi', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('list should get /mail-accounts', async () => {
+    const accounts = [{ id: 1, name: 'acc1' }];
+    mockAxiosInstance.get.mockResolvedValue({ data: accounts });
+
+    const result = await mailAccountsApi.list();
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/mail-accounts');
+    expect(result).toEqual(accounts);
+  });
+
+  it('create should post data to /mail-accounts', async () => {
+    const account = { id: 1, name: 'new' };
+    const createData = {
+      name: 'new',
+      email_address: 'a@b.com',
+      protocol: 'imap',
+      host: 'imap.b.com',
+      port: 993,
+      use_ssl: true,
+      username: 'a@b.com',
+      password: 'secret',
+      forward_to: 'c@d.com',
+    };
+    mockAxiosInstance.post.mockResolvedValue({ data: account });
+
+    const result = await mailAccountsApi.create(createData);
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/mail-accounts', createData);
+    expect(result).toEqual(account);
+  });
+
+  it('update should put data to /mail-accounts/:id', async () => {
+    const account = { id: 5, name: 'updated' };
+    mockAxiosInstance.put.mockResolvedValue({ data: account });
+
+    const result = await mailAccountsApi.update(5, { name: 'updated' });
+
+    expect(mockAxiosInstance.put).toHaveBeenCalledWith('/mail-accounts/5', { name: 'updated' });
+    expect(result).toEqual(account);
+  });
+
+  it('toggle should patch /mail-accounts/:id/toggle', async () => {
+    const account = { id: 3, is_enabled: false };
+    mockAxiosInstance.patch.mockResolvedValue({ data: account });
+
+    const result = await mailAccountsApi.toggle(3);
+
+    expect(mockAxiosInstance.patch).toHaveBeenCalledWith('/mail-accounts/3/toggle');
+    expect(result).toEqual(account);
+  });
+
+  it('pullNow should post to /mail-accounts/:id/pull-now', async () => {
+    const msg = { message: 'Pull initiated' };
+    mockAxiosInstance.post.mockResolvedValue({ data: msg });
+
+    const result = await mailAccountsApi.pullNow(7);
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/mail-accounts/7/pull-now');
+    expect(result).toEqual(msg);
+  });
+
+  it('delete should delete /mail-accounts/:id', async () => {
+    mockAxiosInstance.delete.mockResolvedValue({});
+
+    await mailAccountsApi.delete(4);
+
+    expect(mockAxiosInstance.delete).toHaveBeenCalledWith('/mail-accounts/4');
+  });
+
+  it('test should post config to /mail-accounts/test', async () => {
+    const response = { success: true, message: 'OK' };
+    const config = {
+      host: 'imap.test.com',
+      port: 993,
+      protocol: 'imap',
+      username: 'user',
+      password: 'pass',
+      use_ssl: true,
+    };
+    mockAxiosInstance.post.mockResolvedValue({ data: response });
+
+    const result = await mailAccountsApi.test(config);
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/mail-accounts/test', config);
+    expect(result).toEqual(response);
+  });
+
+  it('testExisting should post to /mail-accounts/:id/test', async () => {
+    const response = { success: true, message: 'Connected' };
+    mockAxiosInstance.post.mockResolvedValue({ data: response });
+
+    const result = await mailAccountsApi.testExisting(10);
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/mail-accounts/10/test');
+    expect(result).toEqual(response);
+  });
+
+  it('autoDetect should post email address to /mail-accounts/auto-detect', async () => {
+    const response = { success: true, suggestions: [{ protocol: 'imap', host: 'imap.x.com' }] };
+    mockAxiosInstance.post.mockResolvedValue({ data: response });
+
+    const result = await mailAccountsApi.autoDetect('user@x.com');
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/mail-accounts/auto-detect', {
+      email_address: 'user@x.com',
+    });
+    expect(result).toEqual(response);
+  });
+});
+
+// ── processingRunsApi ───────────────────────────────────────────────────
+
+describe('processingRunsApi', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('list should get /processing-runs with params', async () => {
+    const paginated = { items: [], total: 0, page: 1, page_size: 20, pages: 0 };
+    mockAxiosInstance.get.mockResolvedValue({ data: paginated });
+
+    const params = { page: 1, page_size: 20, status: 'completed' };
+    const result = await processingRunsApi.list(params);
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/processing-runs', { params });
+    expect(result).toEqual(paginated);
+  });
+
+  it('list should work without params', async () => {
+    const paginated = { items: [], total: 0, page: 1, page_size: 20, pages: 0 };
+    mockAxiosInstance.get.mockResolvedValue({ data: paginated });
+
+    const result = await processingRunsApi.list();
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/processing-runs', { params: undefined });
+    expect(result).toEqual(paginated);
+  });
+
+  it('get should get /processing-runs/:id', async () => {
+    const run = { id: 42, status: 'completed' };
+    mockAxiosInstance.get.mockResolvedValue({ data: run });
+
+    const result = await processingRunsApi.get(42);
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/processing-runs/42');
+    expect(result).toEqual(run);
+  });
+
+  it('getLogs should get /processing-runs/:id/logs with params', async () => {
+    const paginated = { items: [], total: 0, page: 1, page_size: 50, pages: 0 };
+    mockAxiosInstance.get.mockResolvedValue({ data: paginated });
+
+    const params = { page: 2, page_size: 50 };
+    const result = await processingRunsApi.getLogs(42, params);
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/processing-runs/42/logs', { params });
+    expect(result).toEqual(paginated);
+  });
+
+  it('getLogs should work without params', async () => {
+    const paginated = { items: [], total: 0, page: 1, page_size: 20, pages: 0 };
+    mockAxiosInstance.get.mockResolvedValue({ data: paginated });
+
+    const result = await processingRunsApi.getLogs(10);
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/processing-runs/10/logs', {
+      params: undefined,
+    });
+    expect(result).toEqual(paginated);
+  });
+
+  it('listForAccount should get /mail-accounts/:id/processing-runs with params', async () => {
+    const paginated = { items: [], total: 0, page: 1, page_size: 20, pages: 0 };
+    mockAxiosInstance.get.mockResolvedValue({ data: paginated });
+
+    const params = { page: 1, page_size: 20, status: 'failed' };
+    const result = await processingRunsApi.listForAccount(5, params);
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/mail-accounts/5/processing-runs', {
+      params,
+    });
+    expect(result).toEqual(paginated);
+  });
+
+  it('listLogsForAccount should get /mail-accounts/:id/logs with params', async () => {
+    const paginated = { items: [], total: 0, page: 1, page_size: 20, pages: 0 };
+    mockAxiosInstance.get.mockResolvedValue({ data: paginated });
+
+    const params = { page: 1, page_size: 20, level: 'error' };
+    const result = await processingRunsApi.listLogsForAccount(3, params);
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/mail-accounts/3/logs', { params });
+    expect(result).toEqual(paginated);
+  });
+});
+
+// ── gmailApi ────────────────────────────────────────────────────────────
+
+describe('gmailApi', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('getAuthorizeUrl should get /providers/gmail/authorize-url with redirect_uri', async () => {
+    mockAxiosInstance.get.mockResolvedValue({
+      data: { authorization_url: 'https://accounts.google.com/o/oauth2' },
+    });
+
+    const result = await gmailApi.getAuthorizeUrl('http://localhost/callback');
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/providers/gmail/authorize-url', {
+      params: { redirect_uri: 'http://localhost/callback' },
+    });
+    expect(result).toBe('https://accounts.google.com/o/oauth2');
+  });
+
+  it('saveCallback should post code and redirect_uri to /providers/gmail/callback', async () => {
+    const credential = { id: 1, gmail_email: 'test@gmail.com', is_valid: true };
+    mockAxiosInstance.post.mockResolvedValue({ data: credential });
+
+    const result = await gmailApi.saveCallback('authcode', 'http://localhost/callback');
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/providers/gmail/callback', {
+      code: 'authcode',
+      redirect_uri: 'http://localhost/callback',
+    });
+    expect(result).toEqual(credential);
+  });
+
+  it('getCredential should get /providers/gmail-credential', async () => {
+    const credential = { id: 1, gmail_email: 'test@gmail.com', is_valid: true };
+    mockAxiosInstance.get.mockResolvedValue({ data: credential });
+
+    const result = await gmailApi.getCredential();
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/providers/gmail-credential');
+    expect(result).toEqual(credential);
+  });
+
+  it('disconnect should delete /providers/gmail-credential', async () => {
+    mockAxiosInstance.delete.mockResolvedValue({});
+
+    await gmailApi.disconnect();
+
+    expect(mockAxiosInstance.delete).toHaveBeenCalledWith('/providers/gmail-credential');
+  });
+
+  it('sendDebugEmail should post to /providers/gmail/debug-email', async () => {
+    const response = {
+      message: 'Sent',
+      message_id: 'msg1',
+      thread_id: 'thr1',
+      label_ids: ['INBOX'],
+    };
+    mockAxiosInstance.post.mockResolvedValue({ data: response });
+
+    const result = await gmailApi.sendDebugEmail();
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/providers/gmail/debug-email');
+    expect(result).toEqual(response);
+  });
+
+  it('updateImportLabels should put label templates to /providers/gmail-credential/labels', async () => {
+    const credential = { id: 1, import_label_templates: ['Label1'] };
+    mockAxiosInstance.put.mockResolvedValue({ data: credential });
+
+    const result = await gmailApi.updateImportLabels(['Label1']);
+
+    expect(mockAxiosInstance.put).toHaveBeenCalledWith('/providers/gmail-credential/labels', {
+      import_label_templates: ['Label1'],
+    });
+    expect(result).toEqual(credential);
+  });
+});
+
+// ── smtpApi ─────────────────────────────────────────────────────────────
+
+describe('smtpApi', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('get should get /users/smtp-config', async () => {
+    const config = { id: 1, host: 'smtp.test.com', port: 587 };
+    mockAxiosInstance.get.mockResolvedValue({ data: config });
+
+    const result = await smtpApi.get();
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/users/smtp-config');
+    expect(result).toEqual(config);
+  });
+
+  it('save should put config to /users/smtp-config', async () => {
+    const config = { id: 1, host: 'smtp.test.com', port: 587 };
+    const saveData = { host: 'smtp.test.com', port: 587, username: 'user', use_tls: true };
+    mockAxiosInstance.put.mockResolvedValue({ data: config });
+
+    const result = await smtpApi.save(saveData);
+
+    expect(mockAxiosInstance.put).toHaveBeenCalledWith('/users/smtp-config', saveData);
+    expect(result).toEqual(config);
+  });
+
+  it('remove should delete /users/smtp-config', async () => {
+    mockAxiosInstance.delete.mockResolvedValue({});
+
+    await smtpApi.remove();
+
+    expect(mockAxiosInstance.delete).toHaveBeenCalledWith('/users/smtp-config');
+  });
+});
+
+// ── adminApi ────────────────────────────────────────────────────────────
+
+describe('adminApi', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('getStats should get /admin/stats', async () => {
+    const stats = { total_users: 10, total_mail_accounts: 20, total_processing_runs: 100 };
+    mockAxiosInstance.get.mockResolvedValue({ data: stats });
+
+    const result = await adminApi.getStats();
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/admin/stats');
+    expect(result).toEqual(stats);
+  });
+
+  it('listUsers should get /admin/users with skip and limit', async () => {
+    const users = [{ id: 1, email: 'a@b.com' }];
+    mockAxiosInstance.get.mockResolvedValue({ data: users });
+
+    const result = await adminApi.listUsers(10, 50);
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/admin/users', {
+      params: { skip: 10, limit: 50 },
+    });
+    expect(result).toEqual(users);
+  });
+
+  it('listUsers should use defaults for skip and limit', async () => {
+    mockAxiosInstance.get.mockResolvedValue({ data: [] });
+
+    await adminApi.listUsers();
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/admin/users', {
+      params: { skip: 0, limit: 100 },
+    });
+  });
+
+  it('getUser should get /admin/users/:id', async () => {
+    const user = { id: 5, email: 'u@t.com' };
+    mockAxiosInstance.get.mockResolvedValue({ data: user });
+
+    const result = await adminApi.getUser(5);
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/admin/users/5');
+    expect(result).toEqual(user);
+  });
+
+  it('updateUser should put data to /admin/users/:id', async () => {
+    const user = { id: 5, is_active: false };
+    mockAxiosInstance.put.mockResolvedValue({ data: user });
+
+    const result = await adminApi.updateUser(5, { is_active: false });
+
+    expect(mockAxiosInstance.put).toHaveBeenCalledWith('/admin/users/5', { is_active: false });
+    expect(result).toEqual(user);
+  });
+
+  it('deleteUser should delete /admin/users/:id', async () => {
+    mockAxiosInstance.delete.mockResolvedValue({});
+
+    await adminApi.deleteUser(5);
+
+    expect(mockAxiosInstance.delete).toHaveBeenCalledWith('/admin/users/5');
+  });
+
+  it('listPlans should get /admin/plans', async () => {
+    const plans = [{ id: 1, tier: 'free' }];
+    mockAxiosInstance.get.mockResolvedValue({ data: plans });
+
+    const result = await adminApi.listPlans();
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/admin/plans');
+    expect(result).toEqual(plans);
+  });
+
+  it('createPlan should post data to /admin/plans', async () => {
+    const plan = { id: 1, tier: 'pro', name: 'Pro Plan' };
+    const createData = {
+      tier: 'pro',
+      name: 'Pro Plan',
+      price_monthly: 9.99,
+      max_mail_accounts: 10,
+      max_emails_per_day: 1000,
+      check_interval_minutes: 5,
+      support_level: 'email',
+      is_active: true,
+    };
+    mockAxiosInstance.post.mockResolvedValue({ data: plan });
+
+    const result = await adminApi.createPlan(createData);
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/admin/plans', createData);
+    expect(result).toEqual(plan);
+  });
+
+  it('updatePlan should put data to /admin/plans/:id', async () => {
+    const plan = { id: 2, name: 'Updated Plan' };
+    mockAxiosInstance.put.mockResolvedValue({ data: plan });
+
+    const result = await adminApi.updatePlan(2, { name: 'Updated Plan' });
+
+    expect(mockAxiosInstance.put).toHaveBeenCalledWith('/admin/plans/2', { name: 'Updated Plan' });
+    expect(result).toEqual(plan);
+  });
+
+  it('deletePlan should delete /admin/plans/:id', async () => {
+    mockAxiosInstance.delete.mockResolvedValue({});
+
+    await adminApi.deletePlan(3);
+
+    expect(mockAxiosInstance.delete).toHaveBeenCalledWith('/admin/plans/3');
+  });
+
+  it('listProcessingRuns should get /admin/processing-runs with params', async () => {
+    const paginated = { items: [], total: 0, page: 1, page_size: 20, pages: 0 };
+    mockAxiosInstance.get.mockResolvedValue({ data: paginated });
+
+    const params = { page: 1, page_size: 20, user_id: 5 };
+    const result = await adminApi.listProcessingRuns(params);
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/admin/processing-runs', { params });
+    expect(result).toEqual(paginated);
+  });
+
+  it('listProcessingRuns should work without params', async () => {
+    const paginated = { items: [], total: 0, page: 1, page_size: 20, pages: 0 };
+    mockAxiosInstance.get.mockResolvedValue({ data: paginated });
+
+    const result = await adminApi.listProcessingRuns();
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/admin/processing-runs', {
+      params: undefined,
+    });
+    expect(result).toEqual(paginated);
+  });
+
+  it('listProcessingLogs should get /admin/processing-logs with params', async () => {
+    const paginated = { items: [], total: 0, page: 1, page_size: 20, pages: 0 };
+    mockAxiosInstance.get.mockResolvedValue({ data: paginated });
+
+    const params = { page: 1, page_size: 20, level: 'error' };
+    const result = await adminApi.listProcessingLogs(params);
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/admin/processing-logs', { params });
+    expect(result).toEqual(paginated);
+  });
+
+  it('listProcessingLogs should work without params', async () => {
+    const paginated = { items: [], total: 0, page: 1, page_size: 20, pages: 0 };
+    mockAxiosInstance.get.mockResolvedValue({ data: paginated });
+
+    const result = await adminApi.listProcessingLogs();
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/admin/processing-logs', {
+      params: undefined,
+    });
+    expect(result).toEqual(paginated);
+  });
+});
+
+// ── notificationsApi ────────────────────────────────────────────────────
+
+describe('notificationsApi', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('list should get /notifications', async () => {
+    const configs = [{ id: 1, name: 'Notif 1' }];
+    mockAxiosInstance.get.mockResolvedValue({ data: configs });
+
+    const result = await notificationsApi.list();
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/notifications');
+    expect(result).toEqual(configs);
+  });
+
+  it('create should post data to /notifications', async () => {
+    const config = { id: 1, name: 'New Notif', channel: 'email' };
+    const createData = { name: 'New Notif', channel: 'email' };
+    mockAxiosInstance.post.mockResolvedValue({ data: config });
+
+    const result = await notificationsApi.create(createData);
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/notifications', createData);
+    expect(result).toEqual(config);
+  });
+
+  it('update should put data to /notifications/:id', async () => {
+    const config = { id: 2, name: 'Updated' };
+    mockAxiosInstance.put.mockResolvedValue({ data: config });
+
+    const result = await notificationsApi.update(2, { name: 'Updated' });
+
+    expect(mockAxiosInstance.put).toHaveBeenCalledWith('/notifications/2', { name: 'Updated' });
+    expect(result).toEqual(config);
+  });
+
+  it('delete should delete /notifications/:id', async () => {
+    mockAxiosInstance.delete.mockResolvedValue({});
+
+    await notificationsApi.delete(3);
+
+    expect(mockAxiosInstance.delete).toHaveBeenCalledWith('/notifications/3');
+  });
+
+  it('test should post apprise_url to /notifications/test', async () => {
+    const response = { success: true, message: 'Test sent' };
+    mockAxiosInstance.post.mockResolvedValue({ data: response });
+
+    const result = await notificationsApi.test('apprise://slack/webhook');
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/notifications/test', {
+      apprise_url: 'apprise://slack/webhook',
+    });
+    expect(result).toEqual(response);
+  });
+});
+
+// ── adminNotificationsApi ───────────────────────────────────────────────
+
+describe('adminNotificationsApi', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('list should get /admin/notifications', async () => {
+    const configs = [{ id: 1, name: 'Admin Notif' }];
+    mockAxiosInstance.get.mockResolvedValue({ data: configs });
+
+    const result = await adminNotificationsApi.list();
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/admin/notifications');
+    expect(result).toEqual(configs);
+  });
+
+  it('create should post data to /admin/notifications', async () => {
+    const config = { id: 1, name: 'Admin Notif', apprise_url: 'apprise://test' };
+    const createData = { name: 'Admin Notif', apprise_url: 'apprise://test' };
+    mockAxiosInstance.post.mockResolvedValue({ data: config });
+
+    const result = await adminNotificationsApi.create(createData);
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/admin/notifications', createData);
+    expect(result).toEqual(config);
+  });
+
+  it('update should put data to /admin/notifications/:id', async () => {
+    const config = { id: 2, name: 'Updated Admin' };
+    mockAxiosInstance.put.mockResolvedValue({ data: config });
+
+    const result = await adminNotificationsApi.update(2, { name: 'Updated Admin' });
+
+    expect(mockAxiosInstance.put).toHaveBeenCalledWith('/admin/notifications/2', {
+      name: 'Updated Admin',
+    });
+    expect(result).toEqual(config);
+  });
+
+  it('delete should delete /admin/notifications/:id', async () => {
+    mockAxiosInstance.delete.mockResolvedValue({});
+
+    await adminNotificationsApi.delete(4);
+
+    expect(mockAxiosInstance.delete).toHaveBeenCalledWith('/admin/notifications/4');
+  });
+
+  it('test should post apprise_url to /admin/notifications/test', async () => {
+    const response = { success: true, message: 'Admin test sent' };
+    mockAxiosInstance.post.mockResolvedValue({ data: response });
+
+    const result = await adminNotificationsApi.test('apprise://discord/webhook');
+
+    expect(mockAxiosInstance.post).toHaveBeenCalledWith('/admin/notifications/test', {
+      apprise_url: 'apprise://discord/webhook',
+    });
+    expect(result).toEqual(response);
+  });
+});
+
+// ── versionApi ──────────────────────────────────────────────────────────
+
+describe('versionApi', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('get should get /version', async () => {
+    const versionInfo = { version: '1.2.3', build_date: '2024-01-01' };
+    mockAxiosInstance.get.mockResolvedValue({ data: versionInfo });
+
+    const result = await versionApi.get();
+
+    expect(mockAxiosInstance.get).toHaveBeenCalledWith('/version');
+    expect(result).toEqual(versionInfo);
+  });
+});