API Testing Example

An example project demonstrating API testing with Symfony & PHPUnit, including JSON schema matching using the coduo/php-matcher library.

This repository shows practical patterns to write robust API tests — from basic requests to advanced JSON structure assertions — in a real Symfony application context.

🧠 Why this project?

Automated API tests are essential for maintaining confidence when evolving a backend. This example aims to:

• Show clear, real API test patterns with PHPUnit + Symfony.
• Use expressive assertions for JSON responses that go beyond simple exact matching.
• Help developers structure tests for maintainability and clarity.

It’s ideal for:

• Developers learning API testing with Symfony.
• Teams wanting a reference for consistent test conventions.
• People curious about validating API contracts via tests.

---

🚀 Getting started

Requirements

• PHP 8.4+
• Composer
• Symfony CLI (optional but recommended)

Installation

git clone https://github.com/loic425/api-testing-example.git
cd api-testing-example
composer install

▶️ Test it

symfony run vendor/bin/phpunit

🧪 Example tests

Basic GET request test

public function testGetUser()
{
    $response = $this->request('GET', '/api/users/1');
    $this->assertResponseIsSuccessful();
    $this->assertJsonContains(['id' => 1]);
}

Verifying JSON structure using patterns

When you want to validate responses with flexible structure:

$this->assertMatchesPattern(
    [
        'id' => '@integer@',
        'email' => '@string@.isEmail()',
        'createdAt' => '@string@.isDateTime()'
    ],
    $response->toArray()
);

This uses coduo/php-matcher to assert shape and types instead of strict exact matches.

🧩 Project structure

tests/
├── ApiTestCase.php      # Base class with helpers
├── User/
│   ├── GetUserTest.php
│   └── DeleteUserTest.php

ApiTestCase contains common setup and helpers for authenticated requests, JSON assertions, etc.

Each test class focuses on a specific API resource or feature.

📌 Best practices

Here are some tips to make tests reliable and easy to maintain:

🔹 Use dedicated assertion helpers

Abstract response parsing and JSON assertions into reusable helpers in ApiTestCase.

🔹 Test behaviours, not implementation

Assert on the API contract: status codes, expected keys, and semantics — not exact responses that may change format.

🔹 Group related tests in logical files

One test class per API resource or endpoint group.

🛠 Tools and libraries

This project uses:

• Symfony Framework for the backend.
• PHPUnit as the test runner.
• coduo/php-matcher for expressive pattern matching in JSON assertions.

🧠 How does it work?

🧩 ApiTestCase

All API tests extend ApiTestCase.

This class centralizes the testing logic and provides a clean foundation for writing expressive API tests.

1️⃣ Booting Symfony

ApiTestCase extends Symfony’s WebTestCase.

This allows:

• Booting the Symfony kernel
• Creating an HTTP client
• Making real HTTP requests against the application

Each test runs in an isolated environment (APP_ENV=test).

---

2️⃣ Request helper

Instead of manually creating the client and formatting requests in every test, ApiTestCase provides a request() helper.

Example:

$response = $this->request('GET', '/api/books/1');

This method:

• Sends the HTTP request
• Automatically sets JSON headers
• Returns a convenient response object
• Keeps test methods clean and focused

3️⃣ JSON assertions with pattern matching

One key feature of this example project is the integration of coduo/php-matcher.

Instead of asserting exact values:

$this->assertSame('2024-01-01T10:00:00+00:00', $data['createdAt']);

We assert structure and type:

$this->assertMatchesPattern([
    'id' => '@integer@',
    'title' => '@string@',
    'createdAt' => '@string@.isDateTime()'
], $data);

This approach makes tests:

• Less brittle (timestamps and IDs can vary)
• More expressive
• Focused on API contract instead of implementation details