Writing Tests

Rules

1. •Reuse test files - Add tests to existing files when appropriate
2. •Use parametrized tests - Group cases with same expected behavior via @pytest.mark.parametrize
3. •No obvious comments - Code should be self-explanatory
4. •Follow existing style - Match patterns in the existing test suite
5. •Imports at module level - Only import inside functions when absolutely necessary
6. •Reuse fixtures - Use existing fixtures; create new ones only when needed

Test Naming

Name tests using the pattern: test_<what>_<condition>_<outcome>

Examples:

• •test_login_valid_credentials_succeeds
• •test_process_payment_insufficient_funds_raises_error
• •test_parse_json_invalid_input_returns_none

Test Structure

1. •Test all paths - Happy path, edge cases, and error conditions
2. •One assertion focus - Each test should verify one specific behavior
3. •Arrange-Act-Assert - Set up, execute, verify (AAA pattern)

Common Pytest Features

• •Fixtures: @pytest.fixture for shared setup/teardown
• •Marks: @pytest.mark.skip, @pytest.mark.slow, @pytest.mark.integration
• •Mocking: monkeypatch fixture for patching
• •Temp files: tmp_path fixture for file system tests
• •Assertions: Use pytest.raises(ExceptionType) for exception testing