Testing

Test functions that write to stdout/stderr in Go by capturing output with os.Pipe. Learn patterns to avoid deadlocks in concurrent tests.

Return teardown closures from test helpers to manage cleanup elegantly. Learn patterns for temp files, mock servers, and t.Cleanup() usage.

Implement single-method interfaces with function types instead of structs. Master http.HandlerFunc patterns for middlewares, mocks, and adapters.

Clean up pytest test signatures using @pytest.mark.usefixtures to inject implicit fixtures without autouse or unused parameter warnings.

Test HTTP requests in Python with pytest-httpx for full mocking, respx for pattern matching, or VCR.py for recording real responses.

Write readable parametrized tests with pytest.param for better test names, conditional skips, custom IDs, and structured test data.

Mock pydantic_settings in pytest tests by patching the settings class to prevent flaky tests from environment variable dependencies.

Combine session and function-scoped pytest fixtures to avoid expensive test setup while maintaining test isolation and preventing state coupling.

Master Python mocking: patch objects at their import location, not where they're defined, to avoid common unittest.mock pitfalls.

Assert specific mock call arguments while ignoring others using unittest.mock.ANY for flexible test assertions without brittle checks.

Mock chained datetime methods in Python tests using unittest.mock to handle immutable datetime objects without external dependencies.

Create dynamic pytest fixtures with @pytest.fixture(params) to run tests with multiple configurations and parameter combinations.

Combine pytest fixtures with unittest.mock.patch for clean, reusable test mocking patterns that integrate seamlessly with pytest's ecosystem.

Test literal booleans correctly in Python unittest using assertIs instead of assertTrue/assertFalse to avoid truthy/falsy confusion.

Test Python infinite loops safely using daemon threads with timeouts, allowing tests to complete without hanging or blocking execution.