Tdd With Phpunit (Symfony)

Use when

• Driving a feature with RED-GREEN-REFACTOR using PHPUnit 10/11 class-based tests.
• Choosing between TestCase, KernelTestCase and WebTestCase for a new behavior.
• Testing a console command, or an invalid form that must answer 422.
• Swapping an external service for a double through the test container.

Default workflow

1. RED: pick the base class, write the test with #[Test], #[DataProvider] and #[CoversClass], run it and check it fails for the right reason.
2. GREEN: write the minimum code that passes.
3. REFACTOR with the suite green, re-running it after each change.
4. Replace an external boundary with static::getContainer()->set(Service::class, $mock).
5. Test commands with CommandTester, or with runCommand() and assertCommandIsSuccessful() on Symfony 8.1+.
6. Assert invalid form submissions with assertResponseIsUnprocessable().