test: add tests for folder browser APIs and system credentials toggle

Added tests for POST /api/dropbox/list-folders (7 tests) and
POST /api/onedrive/list-folders (7 tests) covering success, subfolder
navigation, empty directories, auth errors, API errors, path
normalization, and alphabetical sorting.

Added view tests for system credentials toggle visibility in Dropbox
setup wizard.

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

tests/test_api_dropbox.py

@@ -412,3 +412,147 @@ class TestSaveDropboxSettings:
         # .env write is best-effort; endpoint should still succeed via DB write
         assert response.status_code == 200
         assert response.json()["status"] == "success"
+
+
+@pytest.mark.unit
+class TestListDropboxFolders:
+    """Tests for list_dropbox_folders endpoint."""
+
+    @patch("app.api.dropbox.requests.post")
+    def test_list_folders_success(self, mock_post, client):
+        """Test successful folder listing at root."""
+        mock_response = Mock()
+        mock_response.status_code = 200
+        mock_response.json.return_value = {
+            "entries": [
+                {".tag": "folder", "name": "Documents", "path_display": "/Documents", "id": "id:1"},
+                {".tag": "folder", "name": "Photos", "path_display": "/Photos", "id": "id:2"},
+                {".tag": "file", "name": "readme.txt", "path_display": "/readme.txt", "id": "id:3"},
+            ],
+            "has_more": False,
+        }
+        mock_post.return_value = mock_response
+
+        response = client.post(
+            "/api/dropbox/list-folders",
+            data={"access_token": "test-token", "path": ""},
+        )
+
+        assert response.status_code == 200
+        data = response.json()
+        assert len(data["folders"]) == 2
+        assert data["folders"][0]["name"] == "Documents"
+        assert data["folders"][1]["name"] == "Photos"
+        assert data["path"] == "/"
+        assert data["has_more"] is False
+
+    @patch("app.api.dropbox.requests.post")
+    def test_list_folders_subfolder(self, mock_post, client):
+        """Test listing folders in a subfolder."""
+        mock_response = Mock()
+        mock_response.status_code = 200
+        mock_response.json.return_value = {
+            "entries": [
+                {".tag": "folder", "name": "Invoices", "path_display": "/Documents/Invoices", "id": "id:4"},
+            ],
+            "has_more": False,
+        }
+        mock_post.return_value = mock_response
+
+        response = client.post(
+            "/api/dropbox/list-folders",
+            data={"access_token": "test-token", "path": "/Documents"},
+        )
+
+        assert response.status_code == 200
+        data = response.json()
+        assert len(data["folders"]) == 1
+        assert data["folders"][0]["path"] == "/Documents/Invoices"
+
+    @patch("app.api.dropbox.requests.post")
+    def test_list_folders_empty(self, mock_post, client):
+        """Test listing folders in an empty directory."""
+        mock_response = Mock()
+        mock_response.status_code = 200
+        mock_response.json.return_value = {"entries": [], "has_more": False}
+        mock_post.return_value = mock_response
+
+        response = client.post(
+            "/api/dropbox/list-folders",
+            data={"access_token": "test-token", "path": "/EmptyFolder"},
+        )
+
+        assert response.status_code == 200
+        assert len(response.json()["folders"]) == 0
+
+    @patch("app.api.dropbox.requests.post")
+    def test_list_folders_unauthorized(self, mock_post, client):
+        """Test listing folders with invalid token returns 401."""
+        mock_response = Mock()
+        mock_response.status_code = 401
+        mock_response.text = "Invalid access token"
+        mock_post.return_value = mock_response
+
+        response = client.post(
+            "/api/dropbox/list-folders",
+            data={"access_token": "bad-token", "path": ""},
+        )
+
+        assert response.status_code == 401
+
+    @patch("app.api.dropbox.requests.post")
+    def test_list_folders_api_error(self, mock_post, client):
+        """Test listing folders when Dropbox API returns an error."""
+        mock_response = Mock()
+        mock_response.status_code = 500
+        mock_response.text = "Internal server error"
+        mock_post.return_value = mock_response
+
+        response = client.post(
+            "/api/dropbox/list-folders",
+            data={"access_token": "test-token", "path": ""},
+        )
+
+        assert response.status_code == 502
+
+    @patch("app.api.dropbox.requests.post")
+    def test_list_folders_root_path_normalization(self, mock_post, client):
+        """Test that '/' is normalized to empty string for Dropbox API."""
+        mock_response = Mock()
+        mock_response.status_code = 200
+        mock_response.json.return_value = {"entries": [], "has_more": False}
+        mock_post.return_value = mock_response
+
+        response = client.post(
+            "/api/dropbox/list-folders",
+            data={"access_token": "test-token", "path": "/"},
+        )
+
+        assert response.status_code == 200
+        # Check the actual API call used empty string for root
+        call_args = mock_post.call_args
+        assert call_args[1]["json"]["path"] == ""
+
+    @patch("app.api.dropbox.requests.post")
+    def test_list_folders_sorted_alphabetically(self, mock_post, client):
+        """Test that folders are returned in alphabetical order."""
+        mock_response = Mock()
+        mock_response.status_code = 200
+        mock_response.json.return_value = {
+            "entries": [
+                {".tag": "folder", "name": "Zebra", "path_display": "/Zebra", "id": "id:1"},
+                {".tag": "folder", "name": "Alpha", "path_display": "/Alpha", "id": "id:2"},
+                {".tag": "folder", "name": "middle", "path_display": "/middle", "id": "id:3"},
+            ],
+            "has_more": False,
+        }
+        mock_post.return_value = mock_response
+
+        response = client.post(
+            "/api/dropbox/list-folders",
+            data={"access_token": "test-token", "path": ""},
+        )
+
+        assert response.status_code == 200
+        names = [f["name"] for f in response.json()["folders"]]
+        assert names == ["Alpha", "middle", "Zebra"]