address backend security and test suggestions

backend/app/tests/test_domain_validator.py

@@ -0,0 +1,63 @@
+import socket
+from unittest.mock import patch
+
+from app.utils.domain_validator import (
+    DomainValidationError,
+    validate_domain,
+    validate_domain_config,
+)
+
+
+class TestValidateDomain:
+    def test_valid_domain_without_dns_check(self):
+        assert validate_domain("example.com", check_dns=False) == (True, None, None)
+
+    def test_domain_longer_than_253_characters_is_rejected(self):
+        domain = f"{'a' * 250}.com"
+
+        valid, message, code = validate_domain(domain, check_dns=False)
+
+        assert valid is False
+        assert "too long" in message
+        assert code == DomainValidationError.TOO_LONG
+
+    def test_dns_resolution_failure_is_reported(self):
+        with patch("app.utils.domain_validator.socket.gethostbyname", side_effect=socket.gaierror):
+            valid, message, code = validate_domain("example.com", check_dns=True)
+
+        assert valid is False
+        assert "could not be resolved" in message
+        assert code == DomainValidationError.DNS_RESOLUTION_FAILED
+
+
+class TestValidateDomainConfig:
+    def test_valid_config(self):
+        result = validate_domain_config(
+            {"name": "example.com", "description": "Primary reporting domain"}
+        )
+
+        assert result == {"valid": True, "errors": {}}
+
+    def test_missing_name_is_invalid(self):
+        result = validate_domain_config({"description": "No name"})
+
+        assert result["valid"] is False
+        assert result["errors"]["name"] == "Domain name is required"
+
+    def test_invalid_domain_name_is_reported(self):
+        result = validate_domain_config({"name": "bad domain"})
+
+        assert result["valid"] is False
+        assert "whitespace" in result["errors"]["name"]
+
+    def test_unsafe_description_is_rejected(self):
+        result = validate_domain_config({"name": "example.com", "description": "<script></script>"})
+
+        assert result["valid"] is False
+        assert "unsafe HTML" in result["errors"]["description"]
+
+    def test_description_length_limit(self):
+        result = validate_domain_config({"name": "example.com", "description": "a" * 501})
+
+        assert result["valid"] is False
+        assert "too long" in result["errors"]["description"]