Testing Knowledge

Testing Knowledge Base

Quick reference for PHP testing patterns, principles, and best practices.

Testing Pyramid

        /\
       /  \     Functional (10%)
      /────\    - E2E, browser tests
     /      \   - Slow, fragile
    /────────\  Integration (20%)
   /          \ - DB, HTTP, queues
  /────────────\Unit (70%)
 /              \- Fast, isolated
/________________\- Business logic

Rule: 70% unit, 20% integration, 10% functional. Invert the pyramid = slow, brittle test suite.

AAA Pattern (Arrange-Act-Assert)

public function test_order_calculates_total_with_discount(): void
{
    // Arrange — set up test data
    $order = new Order(OrderId::generate());
    $order->addItem(new Product('Book', Money::EUR(100)));
    $discount = new PercentageDiscount(10);

    // Act — execute the behavior
    $total = $order->calculateTotal($discount);

    // Assert — verify the outcome
    self::assertEquals(Money::EUR(90), $total);
}

Rules:

• One blank line between sections
• Single Act per test
• Assert behavior, not implementation

Naming Conventions

PHPUnit Style

test_{method}_{scenario}_{expected}

Pest Style

it('calculates total with discount applied')
it('throws exception when confirming shipped order')
it('fails validation for invalid email format')

Test Isolation Principles

DO

• Fresh fixtures per test
• Independent test execution (any order)
• Teardown cleans all state
• Use in-memory implementations

DON'T

• Shared mutable state between tests
• Tests depending on execution order
• Global variables or singletons
• Real external services in unit tests

Quick Quality Checklist

DDD Component Testing

PHP 8.4 Test Patterns

Unit Test Template

<?php

declare(strict_types=1);

namespace Tests\Unit\Domain;

use PHPUnit\Framework\Attributes\CoversClass;
use PHPUnit\Framework\Attributes\Group;
use PHPUnit\Framework\TestCase;

#[Group('unit')]
#[CoversClass(Email::class)]
final class EmailTest extends TestCase
{
    public function test_creates_valid_email(): void
    {
        $email = new Email('user@example.com');

        self::assertSame('user@example.com', $email->value);
    }

    public function test_throws_for_invalid_format(): void
    {
        $this->expectException(InvalidArgumentException::class);

        new Email('invalid');
    }
}

Integration Test Template

<?php

declare(strict_types=1);

namespace Tests\Integration\Infrastructure;

use PHPUnit\Framework\Attributes\Group;
use Tests\DatabaseTestCase;

#[Group('integration')]
final class DoctrineOrderRepositoryTest extends DatabaseTestCase
{
    private OrderRepositoryInterface $repository;

    protected function setUp(): void
    {
        parent::setUp();
        $this->repository = $this->getContainer()->get(OrderRepositoryInterface::class);
    }

    public function test_saves_and_retrieves_order(): void
    {
        // Arrange
        $order = OrderMother::pending();

        // Act
        $this->repository->save($order);
        $found = $this->repository->findById($order->id());

        // Assert
        self::assertNotNull($found);
        self::assertTrue($order->id()->equals($found->id()));
    }
}

Test Doubles Quick Reference

Decision Matrix

Need to verify a call was made?
├── Yes → Mock or Spy
└── No → Need real behavior?
    ├── Yes → Fake
    └── No → Stub

Common Test Smells

Advanced Testing Patterns

Contract Testing (Pact)

When to use: Microservices REST APIs, message-based systems, event schema verification.

Load Testing Patterns

Chaos Testing (Failure Injection)

E2E Distributed Testing

References

For detailed information, load these reference files:

• references/unit-testing.md — Unit test patterns and examples
• references/integration-testing.md — Integration test setup and patterns
• references/ddd-testing.md — Testing DDD components (VO, Entity, Aggregate, Service)
• references/advanced-testing.md — Contract testing (Pact), chaos testing, load testing patterns (ramp-up, spike, soak), E2E distributed testing