phpunit-test

PHPUnit Testing Rules

Test Structure Requirements

// Always extend TestCase
class ProductServiceTest extends TestCase 
{
    // Use typed properties
    private ProductService $subject;
    private MockObject $repository;
    
    // Always use return type void for setUp/tearDown
    protected function setUp(): void 
    {
        // Create mocks using createMock()
        $this->repository = $this->createMock(RepositoryInterface::class);
        $this->subject = new ProductService($this->repository);
    }
    
    // Test methods: prefix with test or use @test annotation
    // Use descriptive method names
    /** @test */
    public function getProductReturnsCorrectDataForValidId(): void 
    {
        // Always follow Arrange-Act-Assert pattern
        
        // Arrange
        $id = 'valid-id';
        $expected = ['id' => 'valid-id', 'name' => 'Product'];
        
        $this->repository->method('findById')
            ->with($id)
            ->willReturn($expected);
        
        // Act
        $result = $this->subject->getProduct($id);
        
        // Assert - use specific assertions
        $this->assertSame($expected, $result);
    }
}

Refactoring Guidelines

When refactoring tests, use this incremental approach:

1. Create a refactoring plan before starting
2. Break changes into logical steps:

   Step 1: Extract hardcoded strings to constants
   Step 2: Create required mocks
   Step 3: Fix assertion methods
   Step 4: Implement proper exception testing
   

3. Complete one step at a time before moving to the next

Mock Objects

// Good - explicit mock creation and configuration
$repository = $this->createMock(RepositoryInterface::class);
$repository->method('findById')
    ->with('valid-id')
    ->willReturn(['id' => 'valid-id', 'name' => 'Product']);

// Bad - unclear expectations
$repository = $this->createMock(Repository::class);
$repository->expects($this->any())
    ->method('findById')
    ->willReturn($data);