PHPUnit Best Practices

Comprehensive testing best practices guide for PHPUnit applications, maintained by pentiminax. Contains 40 rules across 8 categories, prioritized by impact to guide automated test generation, refactoring, and code review.

When to Apply

Reference these guidelines when:

• Writing new PHPUnit test classes or test methods
• Reviewing test code for quality and consistency
• Refactoring existing test suites
• Configuring PHPUnit XML settings
• Setting up code coverage and test organization

Rule Categories by Priority

Quick Reference

1. Principles & Patterns (CRITICAL)

• rules/principle-aaa-pattern.md - Structure tests with Arrange-Act-Assert
• rules/principle-first-fast.md - Keep tests fast
• rules/principle-first-isolated.md - Ensure tests are independent
• rules/principle-first-repeatable.md - Make tests deterministic
• rules/principle-first-self-validating.md - Tests must have clear pass/fail
• rules/principle-first-timely.md - Write tests alongside production code
• rules/principle-dry-vs-damp.md - Balance DRY and readability in tests

2. Coding Standards (CRITICAL)

• rules/standard-strict-types.md - Declare strict_types=1 in test files
• rules/standard-final-classes.md - Make test classes final
• rules/standard-snake-case-methods.md - Use snake_case for test method names
• rules/standard-psr4-naming.md - Follow PSR-4 naming and namespace conventions
• rules/standard-psr12-formatting.md - Apply PSR-12 code formatting
• rules/standard-this-over-self.md - Use $this over self:: for assertions
• rules/standard-visibility-type-hints.md - Explicit visibility and type hints

3. Test Attributes (HIGH)

• rules/attr-test-attribute.md - Use #[Test] attribute with it_ prefix
• rules/attr-covers-class.md - Use #[CoversClass] for coverage boundaries
• rules/attr-uses-class.md - Use #[UsesClass] for dependency documentation
• rules/attr-size-categories.md - Categorize tests by size
• rules/attr-group.md - Use #[Group] for arbitrary categorization
• rules/attr-no-annotations.md - Prefer PHP 8 attributes over PHPDoc annotations

4. Data Management (HIGH)

• rules/data-provider.md - Use #[DataProvider] for multiple scenarios
• rules/data-provider-external.md - Use #[DataProviderExternal] for shared data
• rules/data-test-with.md - Use #[TestWith] for inline datasets
• rules/data-factory-method.md - Factory methods for SUT instantiation
• rules/data-direct-instantiation.md - Direct instantiation for simple constructors

5. Test Documentation (MEDIUM)

• rules/doc-testdox.md - Use TestDox for executable specifications
• rules/doc-testdox-attribute.md - #[TestDox] attribute for custom display
• rules/doc-readable-names.md - Readable test names as specifications

6. Mocking (MEDIUM)

• rules/mock-chicago-vs-london.md - Chicago vs London TDD schools
• rules/mock-prophecy.md - Prophecy for expressive test doubles
• rules/mock-avoid-over-mocking.md - Avoid over-mocking internal dependencies

7. Integration Testing (MEDIUM)

• rules/integration-smoke-http.md - HTTP controller smoke tests
• rules/integration-smoke-cli.md - CLI command smoke tests
• rules/integration-performance.md - Performance-aware test setup
• rules/integration-singleton.md - Singletons for stateless services
• rules/integration-transactions.md - Database transactions for test cleanup

8. Configuration (LOW-MEDIUM)

• rules/config-testsuites.md - Organize tests in named suites
• rules/config-strictness.md - Enable strict mode settings
• rules/config-source-coverage.md - Source directory for coverage analysis
• rules/config-order-by.md - Test execution ordering strategies
• rules/config-cache.md - Cache directory for performance
• rules/config-stop-on-failure.md - Stop on first failure for fast feedback

How to Use

Read individual rule files for detailed explanations and code examples:

• rules/principle-aaa-pattern.md
• rules/standard-final-classes.md

Each rule file contains:

• Brief explanation of why it matters
• Incorrect code example with explanation
• Correct code example with explanation
• Additional context and references