Phpunit

PHPUnit

Test behavior, not implementation. Tests are executable documentation — if the test name doesn't explain what the code does, rewrite it.

PHPUnit is PHP's standard testing framework. It uses test case classes extending TestCase, setUp()/tearDown() for fixtures, and a full assertion API. All patterns target PHPUnit 11+ on PHP 8.5+. Use PHP 8 attributes exclusively — annotations are deprecated in 11, removed in 12.

References

• Assertion catalog, constraints, exception expectations → [${CLAUDE_SKILL_DIR}/references/assertions.md] — Full

assertion API grouped by category, constraint system, custom assertions

• Test doubles — stubs, mocks, MockBuilder → [${CLAUDE_SKILL_DIR}/references/mocking.md] — createStub vs

createMock, return config, invocation matchers, argument constraints, MockBuilder

• Data providers — static, named, generators → [${CLAUDE_SKILL_DIR}/references/data-providers.md]

— #[DataProvider], #[TestWith], named datasets, generator providers, external providers

• phpunit.xml structure, test suites, source config → [${CLAUDE_SKILL_DIR}/references/configuration.md] — XML

elements, strict settings, source element, coverage reports, execution order

Test Structure

Discovery and Naming

• Files: *Test.php in configured test directories. Mirror source structure: src/Service/PaymentService.php →

tests/Unit/Service/PaymentServiceTest.php.

• Classes: final class PaymentServiceTest extends TestCase. Always final.
• Methods: test prefix or #[Test] attribute. Describe the behavior: testReturnsEmptyCollectionWhenNoResults

not testSearch.

• One test class per production class. Split into Unit/Integration directories.

Arrange-Act-Assert

Structure every test in three phases:

public function testUserCreationSetsDefaults(): void
{
    // Arrange
    $data = ['name' => 'Alice', 'email' => 'alice@example.com'];

    // Act
    $user = User::fromArray($data);

    // Assert
    $this->assertSame('Alice', $user->getName());
    $this->assertTrue($user->isActive());
    $this->assertSame([], $user->getRoles());
}

• One act per test. If you need multiple acts, write multiple tests.
• Comments optional when phases are obvious. Add them when the test is long enough that phases aren't immediately

clear.

Test Granularity

• One concept per test. Multiple assertions are fine when they verify the same behavior. Separate tests when

behaviors are independent.

• Fast by default. Unit tests should run in milliseconds. Gate slow tests behind groups: #[Group('slow')].
• Isolation is mandatory. Tests must not depend on execution order or shared mutable state. Each test sets up its

own world.

Fixtures

setUp() / tearDown()

• setUp() runs before each test method on a fresh instance. Create the SUT and its stubs here.
• tearDown() runs after each test. Only needed for external resources (files, sockets, DB connections). Not needed

for plain object cleanup.

• setUpBeforeClass() / tearDownAfterClass() run once per class. Use for expensive shared resources (DB

connections). Store in static properties.

final class PaymentServiceTest extends TestCase
{
    private PaymentService $service;
    private Gateway&Stub $gateway;

    protected function setUp(): void
    {
        $this->gateway = $this->createStub(Gateway::class);
        $this->service = new PaymentService($this->gateway);
    }
}

Fixture Lifecycle

• setUpBeforeClass() — Class scope; once before first test
• setUp() — Method scope; before each test
• assertPreConditions() — Method scope; after setUp, before test
• assertPostConditions() — Method scope; after test, before tearDown
• tearDown() — Method scope; after each test
• tearDownAfterClass() — Class scope; once after last test

• Call parent::setUp() when extending abstract test cases — otherwise parent fixture setup is silently skipped.
• Use #[Before] / #[After] attributes when multiple setup methods are needed (avoids fragile parent::setUp()

chains).

Data Providers

Basic Usage

use PHPUnit\Framework\Attributes\DataProvider;

#[DataProvider('additionCases')]
public function testAdd(int $a, int $b, int $expected): void
{
    $this->assertSame($expected, $a + $b);
}

public static function additionCases(): array
{
    return [
        'zeros'        => [0, 0, 0],
        'positive sum' => [1, 2, 3],
        'negative'     => [-1, 1, 0],
    ];
}

• Providers must be public static. Non-static providers are removed in PHPUnit 11.
• Always use named datasets — string keys produce readable failure output.
• Use #[DataProvider] attribute, not @dataProvider annotation.

Inline Data

For small, simple datasets — no provider method needed:

use PHPUnit\Framework\Attributes\TestWith;

#[TestWith([0, 0, 0])]
#[TestWith([1, 2, 3])]
#[TestWith([-1, 1, 0])]
public function testAdd(int $a, int $b, int $expected): void
{
    $this->assertSame($expected, $a + $b);
}

Generator Providers

For large or computed datasets:

public static function boundaryCases(): Generator
{
    yield 'min int' => [PHP_INT_MIN, 0, PHP_INT_MIN];
    yield 'max int' => [PHP_INT_MAX, 0, PHP_INT_MAX];
}

Provider Rules

• Data must be scalar or immutable — no service objects or complex graphs in providers.
• No mock objects in providers — framework isn't initialized during provider execution.
• Empty providers are forbidden in PHPUnit 11 — throws InvalidDataProviderException.
• Multiple providers can be stacked on one test method — datasets are combined.

See ${CLAUDE_SKILL_DIR}/references/data-providers.md for external providers, TestDox integration, and edge cases.

Assertions

Core Assertions

$this->assertSame($expected, $actual);        // Strict === (preferred)
$this->assertEquals($expected, $actual);       // Loose == (use sparingly)
$this->assertTrue($condition);
$this->assertFalse($condition);
$this->assertNull($value);
$this->assertInstanceOf(Expected::class, $obj);
$this->assertCount(3, $collection);
$this->assertEmpty($collection);
$this->assertArrayHasKey('key', $array);
$this->assertContains($needle, $haystack);     // Strict comparison

• Prefer assertSame() over assertEquals() — strict type comparison catches more bugs.
• Multiple assertions per test are fine when they verify the same behavior.

String Assertions

$this->assertStringStartsWith('Error:', $message);
$this->assertStringEndsWith('.php', $filename);
$this->assertStringContainsString('needle', $haystack);
$this->assertMatchesRegularExpression('/^\d{4}-\d{2}$/', $date);

Float Comparison

$this->assertEqualsWithDelta(3.14, $result, 0.01);

Exception Testing

public function testThrowsOnInvalidInput(): void
{
    $this->expectException(InvalidArgumentException::class);
    $this->expectExceptionMessage('must be positive');

    $calculator->divide(1, 0);
}

• Call expectException() before the throwing code — it sets up the expectation.
• Use expectExceptionMessage() when the exception type is broad — validates the message contains the substring.
• Use expectExceptionMessageMatches() for regex matching.

Deprecation / Error Expectations

public function testTriggersDeprecation(): void
{
    $this->expectUserDeprecationMessage('use newMethod() instead');

    $service->oldMethod();
}

See ${CLAUDE_SKILL_DIR}/references/assertions.md for the full assertion catalog, constraint system, and format string assertions.

Mocking

Stubs vs Mocks

• Stub (createStub()) — controls return values. No call verification.
• Mock (createMock()) — verifies interactions (method called, arguments matched).

Use stubs by default. Use mocks only when verifying that a side effect occurred.

Creating Stubs

$repo = $this->createStub(UserRepository::class);
$repo->method('find')->willReturn(new User(name: 'Alice'));

$service = new UserService($repo);
$result = $service->getUser(1);

$this->assertSame('Alice', $result->name);

Shorthand for multiple methods:

$repo = $this->createConfiguredStub(UserRepository::class, [
    'find'   => new User(name: 'Alice'),
    'exists' => true,
]);

Creating Mocks

$logger = $this->createMock(Logger::class);
$logger->expects($this->once())
    ->method('error')
    ->with($this->stringContains('payment failed'));

$service = new PaymentService($logger);
$service->process($invalidPayment);

Return Value Configuration

$stub->method('fetch')->willReturn('value');              // Fixed value
$stub->method('fetch')->willReturn('a', 'b', 'c');       // Consecutive values
$stub->method('fetch')->willReturnArgument(0);            // Return first arg
$stub->method('fetch')->willReturnSelf();                 // Fluent interface
$stub->method('fetch')->willReturnCallback(fn ($id) => "item-{$id}");
$stub->method('fetch')->willThrowException(new RuntimeException('fail'));
$stub->method('fetch')->willReturnMap([
    ['key1', 'value1'],
    ['key2', 'value2'],
]);

Mocking Rules

• Mock at boundaries. Mock external services, databases, filesystems, clocks — not internal functions.
• Don't mock what you own when a fake or in-memory implementation is available.
• Prefer dependency injection over complex mock setup. Pass collaborators as constructor parameters, stub in tests.
• Never mock the thing you're testing. If you need to mock part of the SUT, the SUT has too many responsibilities —

split it.

• Favour interfaces over classes for test doubles — fewer limitations, better design.
• Do not call expects() on stubs — deprecated in 11, error in 12.

See ${CLAUDE_SKILL_DIR}/references/mocking.md for MockBuilder, intersection types, invocation matchers, and PHP 8.4 property hooks.

Attributes

PHPUnit 11 uses PHP 8 attributes exclusively. All attributes are in the PHPUnit\Framework\Attributes namespace.

Test Metadata

• #[Test] — Mark non-test* method as a test
• #[DataProvider('method')] — Connect a data provider
• #[DataProviderExternal(Class::class, 'method')] — External data provider
• #[TestWith([args])] — Inline data provider
• #[TestDox('description')] — Custom TestDox description
• #[Depends('testMethod')] — Declare test dependency
• #[Group('name')] — Assign to group
• #[Ticket('PROJ-123')] — Link to issue tracker

Skip / Conditional

• #[RequiresPhp('>= 8.4')] — Skip if PHP version doesn't match
• #[RequiresPhpExtension('pdo_pgsql')] — Skip if extension missing
• #[RequiresOperatingSystemFamily('Linux')] — Skip on other OS
• #[RequiresFunction('sodium_crypto_sign')] — Skip if function missing
• #[RequiresMethod(PDO::class, 'sqliteCreateFunction')] — Skip if method missing

Coverage

• #[CoversClass(ClassName::class)] — Test covers this class
• #[CoversFunction('functionName')] — Test covers this function
• #[CoversMethod(ClassName::class, 'method')] — Test covers this method
• #[CoversNothing] — Test contributes no coverage (integration tests)
• #[UsesClass(ClassName::class)] — Allowed but not covered dependency
• #[UsesFunction('functionName')] — Allowed but not covered function

Fixture

• #[Before] — Run method before each test (alternative to setUp)
• #[After] — Run method after each test (alternative to tearDown)
• #[BeforeClass] — Run static method before first test
• #[AfterClass] — Run static method after last test
• #[BackupGlobals(true)] — Backup/restore globals for this test
• #[BackupStaticProperties(true)] — Backup/restore static properties

Test Behavior

• #[DoesNotPerformAssertions] — Suppress risky test warning
• #[RunInSeparateProcess] — Isolate in separate PHP process
• #[RunTestsInSeparateProcesses] — All tests in class run isolated
• #[Small] / #[Medium] / #[Large] — Time limit enforcement (1s/10s/60s)

Test Organization

Directory Structure

tests/
├── Unit/                     # Fast, isolated, no I/O
│   ├── Service/
│   │   └── PaymentServiceTest.php
│   └── Model/
│       └── UserTest.php
├── Integration/              # Real dependencies, slower
│   └── Repository/
│       └── UserRepositoryTest.php
└── bootstrap.php             # Autoloader for tests

• Mirror source directory structure under tests/Unit/ and tests/Integration/.
• Unit tests — no database, no filesystem, no network. Mock all boundaries.
• Integration tests — real dependencies. Mark with #[CoversNothing] to avoid polluting coverage metrics.

Test Suites

Define in phpunit.xml for selective execution:

    
        tests/Unit
    
    
        tests/Integration
    

Run subsets: phpunit --testsuite unit, phpunit --group slow.

Configuration

Recommended phpunit.xml

    
        
            tests/Unit
        
        
            tests/Integration
        
    
    
        
            src
        
    

Key Configuration Choices

• executionOrder="depends,random" — randomize test order to catch hidden dependencies while respecting explicit

#[Depends].

• beStrictAboutTestsThatDoNotTestAnything="true" — flag tests without assertions as risky.
• failOnDeprecation="true" — catch deprecations from your code early.
• ` with restrictDeprecations` — only surface issues from your code, not vendor dependencies.
• cacheDirectory — add .phpunit.cache to .gitignore.

Code Coverage

Requires PCOV or Xdebug extension:

phpunit --coverage-html build/coverage --coverage-clover build/clover.xml

Use #[CoversClass] and #[UsesClass] attributes to target coverage precisely. With beStrictAboutCoverageMetadata="true", tests without coverage attributes are risky.

See ${CLAUDE_SKILL_DIR}/references/configuration.md for the full XML reference, coverage report types, and execution order options.

Application

When writing tests: apply all conventions silently — don't narrate each rule being followed. Match the project's existing test style. If an existing codebase contradicts a convention, follow the codebase and flag the divergence once.

When reviewing tests: cite the specific issue and show the fix inline. Don't lecture — state what's wrong and how to fix it.

Bad:  "According to PHPUnit best practices, you should use createStub
       instead of createMock when you don't need expectations..."
Good: "createMock → createStub (no expects() call, stub is sufficient)"

Integration

The php skill governs language choices; this skill governs PHPUnit testing decisions. The coding skill governs workflow (discovery, planning, verification).

Test behavior, not implementation. When in doubt, mock less.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: xobotyi
• Source: xobotyi/cc-foundry
• License: MIT

Install and usage instructions live in the source repository linked above.