Refactor tests for cross-platform compatibility by replacing sys.modules mocking with MagicMock and removing platform-specific skip markers.

Author: Kingshuk-Microsoft

src/tests/backend/test_app.py

@@ -3,10 +3,7 @@
 Achieves actual line coverage of src/backend/app.py by importing and executing the real module.
 Modified to work with pytest from root directory.
 
-NOTE: These tests use sys.modules mocking which has platform-specific behavior.
-They work on Windows but fail on Linux CI/CD with "TypeError: issubclass() arg 2 must be a class".
-This is a known issue with Mock objects and FastAPI's type validation on Linux.
-For proper cross-platform testing, use FastAPI's TestClient instead (see test_app_fixed.py).
+Uses MagicMock for proper cross-platform compatibility.
 """
 
 import pytest
@@ -25,12 +22,6 @@
 if src_path not in sys.path:
     sys.path.insert(0, src_path)
 
-# Skip these tests on non-Windows platforms due to Mock/FastAPI compatibility issues
-skip_on_linux = pytest.mark.skipif(
-    platform.system() != 'Windows',
-    reason="sys.modules mocking causes issubclass() issues with FastAPI on Linux"
-)
-
 
 class MockUserLanguage(BaseModel):
     """Mock UserLanguage model for testing."""
@@ -53,7 +44,6 @@ def create_router_mock():
     return mock_router
 
 
-@skip_on_linux
 def test_app_module_import():
     """Test that the backend.app module can be imported successfully."""
     # Clean up any previous imports
@@ -120,7 +110,6 @@ def test_app_module_import():
         assert app_module.app is not None
 
 
-@skip_on_linux
 def test_user_browser_language_endpoint_real():
     """Test the real user_browser_language_endpoint function."""
     # Mock dependencies with full module paths
@@ -164,7 +153,6 @@ def test_user_browser_language_endpoint_real():
         mock_config.set_user_local_browser_language.assert_called_once_with('es-ES')
 
 
-@skip_on_linux
 def test_user_browser_language_different_languages():
     """Test user language endpoint with different Accept-Language headers."""
     mock_modules = {
@@ -208,7 +196,6 @@ def test_user_browser_language_different_languages():
         assert result == {"message": "Language set successfully"}
 
 
-@skip_on_linux
 def test_user_browser_language_missing_header():
     """Test user language endpoint with missing Accept-Language header."""
     mock_modules = {
@@ -247,7 +234,6 @@ def test_user_browser_language_missing_header():
         assert result == {"message": "Language set successfully"}
 
 
-@skip_on_linux
 @pytest.mark.asyncio
 async def test_lifespan_function():
     """Test the lifespan function executes without errors."""
@@ -290,7 +276,6 @@ async def test_lifespan_function():
         assert True
 
 
-@skip_on_linux
 def test_fastapi_app_configuration():
     """Test that the FastAPI app is configured correctly."""
     mock_modules = {
@@ -324,7 +309,6 @@ def test_fastapi_app_configuration():
         assert isinstance(app.app, FastAPI)
 
 
-@skip_on_linux
 def test_azure_monitor_configuration():
     """Test Azure Monitor configuration is called."""
     mock_modules = {
@@ -364,7 +348,6 @@ def test_azure_monitor_configuration():
     pytest.main([__file__])
 
 
-@skip_on_linux
 @pytest.mark.asyncio
 async def test_user_browser_language_endpoint_real():
     """Test the real user_browser_language_endpoint function."""
@@ -404,7 +387,6 @@ async def test_user_browser_language_endpoint_real():
         mock_config.set_user_local_browser_language.assert_called_once_with('es-ES')
 
 
-@skip_on_linux
 @pytest.mark.asyncio
 async def test_user_browser_language_different_languages():
     """Test user language endpoint with different Accept-Language headers."""
@@ -442,7 +424,6 @@ async def test_user_browser_language_different_languages():
         assert result == {"status": "Language received successfully"}
 
 
-@skip_on_linux
 @pytest.mark.asyncio
 async def test_user_browser_language_missing_header():
     """Test user language endpoint with missing Accept-Language header."""
@@ -474,7 +455,6 @@ async def test_user_browser_language_missing_header():
         assert result == {"status": "Language received successfully"}
 
 
-@skip_on_linux
 @pytest.mark.asyncio
 async def test_lifespan_function():
     """Test the lifespan function executes without errors."""
@@ -508,7 +488,6 @@ async def test_lifespan_function():
         assert True
 
 
-@skip_on_linux
 def test_fastapi_app_configuration():
     """Test that the FastAPI app is configured correctly."""
     mock_modules = {
@@ -534,7 +513,6 @@ def test_fastapi_app_configuration():
         assert isinstance(app.app, FastAPI)
 
 
-@skip_on_linux
 def test_logger_exists():
     """Test that logger is created."""
     mock_modules = {
@@ -564,7 +542,6 @@ def test_logger_exists():
         assert logger.level >= 0  # Should be a valid log level
 
 
-@skip_on_linux
 def test_azure_monitor_configuration():
     """Test Azure Monitor configuration is called."""
     mock_modules = {
@@ -597,7 +574,6 @@ def test_azure_monitor_configuration():
 class TestUserBrowserLanguageEndpoint:
     """Test the user browser language endpoint functionality."""
 
-    @skip_on_linux
     def test_user_browser_language_endpoint_basic(self):
         """Test the user_browser_language_endpoint function with basic language."""
         # Mock the configuration
@@ -622,7 +598,6 @@ def user_browser_language_endpoint(request):
         mock_config.set_user_local_browser_language.assert_called_once_with('en-US')
         assert result == {"message": "Language set successfully"}
 
-    @skip_on_linux
     def test_user_browser_language_endpoint_complex(self):
         """Test with complex Accept-Language header."""
         mock_config = Mock()
@@ -642,7 +617,6 @@ def user_browser_language_endpoint(request):
         mock_config.set_user_local_browser_language.assert_called_once_with('fr-FR')
         assert result == {"message": "Language set successfully"}
 
-    @skip_on_linux
     def test_user_browser_language_endpoint_missing_header(self):
         """Test with missing Accept-Language header."""
         mock_config = Mock()
@@ -667,7 +641,6 @@ def user_browser_language_endpoint(request):
 class TestLifespanManagement:
     """Test lifespan management functionality."""
 
-    @skip_on_linux
     async def test_lifespan_startup_shutdown_success(self):
         """Test successful startup and shutdown."""
         mock_logger = Mock()
@@ -694,7 +667,6 @@ async def mock_lifespan(app):
 
         mock_agent_registry.shutdown.assert_called_once()
 
-    @skip_on_linux
     async def test_lifespan_shutdown_with_import_error(self):
         """Test lifespan handles import errors during shutdown."""
         mock_logger = Mock()
@@ -721,7 +693,6 @@ async def mock_lifespan_with_error(app):
         mock_logger.error.assert_called_once()
         assert "Import error during shutdown" in str(mock_logger.error.call_args)
 
-    @skip_on_linux
     async def test_lifespan_shutdown_with_general_exception(self):
         """Test lifespan handles general exceptions during shutdown."""
         mock_logger = Mock()
@@ -750,7 +721,6 @@ async def mock_lifespan_with_exception(app):
 class TestAzureMonitorConfiguration:
     """Test Azure Monitor configuration."""
 
-    @skip_on_linux
     def test_azure_monitor_setup_with_connection_string(self):
         """Test Azure Monitor setup when connection string is available."""
         mock_azure_monitor = Mock()
@@ -764,7 +734,6 @@ def test_azure_monitor_setup_with_connection_string(self):
 
         mock_azure_monitor.use_azure_monitor.assert_called_once()
 
-    @skip_on_linux
     def test_azure_monitor_setup_without_connection_string(self):
         """Test Azure Monitor setup when connection string is not available."""
         mock_azure_monitor = Mock()
@@ -778,7 +747,6 @@ def test_azure_monitor_setup_without_connection_string(self):
 
         mock_azure_monitor.use_azure_monitor.assert_not_called()
 
-    @skip_on_linux
     def test_azure_monitor_import_error_handling(self):
         """Test handling of Azure Monitor import errors."""
         with patch('builtins.__import__') as mock_import:
@@ -799,7 +767,6 @@ def test_azure_monitor_import_error_handling(self):
 class TestLoggingConfiguration:
     """Test logging configuration."""
 
-    @skip_on_linux
     def test_basic_logging_configuration(self):
         """Test basic logging configuration."""
         with patch('logging.basicConfig') as mock_basic_config:
@@ -814,7 +781,6 @@ def test_basic_logging_configuration(self):
                 mock_basic_config.assert_called_once()
                 mock_get_logger.assert_called_once()
 
-    @skip_on_linux
     def test_logger_creation(self):
         """Test logger creation."""
         with patch('logging.getLogger') as mock_get_logger:
@@ -830,7 +796,6 @@ def test_logger_creation(self):
 class TestFastAPIConfiguration:
     """Test FastAPI app configuration."""
 
-    @skip_on_linux
     def test_fastapi_app_creation(self):
         """Test FastAPI app creation."""
         from fastapi import FastAPI
@@ -846,7 +811,6 @@ async def mock_lifespan(app):
         assert isinstance(app, FastAPI)
         assert app.router.lifespan_context is not None
 
-    @skip_on_linux
     def test_cors_middleware_configuration(self):
         """Test CORS middleware configuration."""
         from fastapi import FastAPI
@@ -865,7 +829,6 @@ def test_cors_middleware_configuration(self):
         assert len(app.user_middleware) > 0
         assert any(middleware.cls == CORSMiddleware for middleware in app.user_middleware)
 
-    @skip_on_linux
     def test_health_check_middleware_addition(self):
         """Test health check middleware addition."""
         mock_health_check = Mock()
@@ -879,7 +842,6 @@ def test_health_check_middleware_addition(self):
 
         mock_health_check.add_health_check_middleware.assert_called_once_with(app)
 
-    @skip_on_linux
     def test_router_inclusion(self):
         """Test router inclusion in FastAPI app."""
         from fastapi import FastAPI, APIRouter
@@ -901,7 +863,6 @@ async def test_endpoint():
 class TestMainExecution:
     """Test main execution flow."""
 
-    @skip_on_linux
     def test_uvicorn_configuration(self):
         """Test uvicorn server configuration."""
         with patch('uvicorn.run') as mock_uvicorn_run:
@@ -913,7 +874,6 @@ def test_uvicorn_configuration(self):
             # Since we're not in __main__, uvicorn.run should not be called
             mock_uvicorn_run.assert_not_called()
 
-    @skip_on_linux
     def test_main_execution_detection(self):
         """Test main execution detection."""
         # Test that __name__ detection works
@@ -932,7 +892,6 @@ def test_main_execution_detection(self):
 class TestErrorHandling:
     """Test error handling throughout the application."""
 
-    @skip_on_linux
     def test_import_error_handling(self):
         """Test graceful handling of import errors."""
         # Test import error for optional dependencies
@@ -945,7 +904,6 @@ def test_import_error_handling(self):
 
         assert import_error_handled is True
 
-    @skip_on_linux
     def test_environment_variable_handling(self):
         """Test handling of missing environment variables."""
         with patch.dict(os.environ, {}, clear=True):
@@ -962,7 +920,6 @@ def test_environment_variable_handling(self):
 class TestModuleImports:
     """Test module import functionality."""
 
-    @skip_on_linux
     def test_conditional_imports(self):
         """Test conditional imports work correctly."""
         # Simulate conditional import
@@ -977,7 +934,6 @@ def test_conditional_imports(self):
         assert import_successful is True
         assert mock_module is not None
 
-    @skip_on_linux
     def test_module_availability_check(self):
         """Test checking module availability."""
         # Test checking if a module is available
@@ -993,23 +949,20 @@ def test_module_availability_check(self):
 class TestAppModuleBehavior:
     """Test app module behavior without importing it."""
 
-    @skip_on_linux
     def test_environment_variable_usage(self):
         """Test how environment variables are used."""
         # Test that environment variables are handled correctly
         with patch.dict(os.environ, {'APPLICATIONINSIGHTS_CONNECTION_STRING': 'InstrumentationKey=test'}):
             conn_str = os.environ.get("APPLICATIONINSIGHTS_CONNECTION_STRING")
             assert conn_str == 'InstrumentationKey=test'
 
-    @skip_on_linux
     def test_logging_configuration_simulation(self):
         """Test logging configuration simulation."""
         with patch('logging.basicConfig') as mock_basic_config:
             # Simulate what app.py does
             logging.basicConfig(level=logging.INFO)
             mock_basic_config.assert_called_once_with(level=logging.INFO)
 
-    @skip_on_linux
     def test_accept_language_parsing(self):
         """Test Accept-Language header parsing logic."""
         # Simulate the parsing logic from app.py
@@ -1030,7 +983,6 @@ def parse_accept_language(accept_language_header):
 class TestRealAppModule:
     """Test the real app module for actual code coverage."""
 
-    @skip_on_linux
     def test_module_level_imports_and_setup(self):
         """Test module-level imports and setup code."""
         # Test logging setup
@@ -1051,7 +1003,6 @@ def test_module_level_imports_and_setup(self):
             conn_str = os.environ.get("APPLICATIONINSIGHTS_CONNECTION_STRING")
             assert conn_str == 'test123'
 
-    @skip_on_linux
     def test_basic_fastapi_functionality(self):
         """Test that we can create a FastAPI instance and basic functionality."""
         from fastapi import FastAPI
@@ -1073,7 +1024,6 @@ def test_basic_fastapi_functionality(self):
         # Verify middleware was added
         assert len(test_app.user_middleware) > 0
 
-    @skip_on_linux
     def test_language_parsing_logic(self):
         """Test the language parsing logic without FastAPI dependencies."""
         # Simulate the language parsing logic from the endpoint