What is CodeIgniter 4 testing mock services?
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Advanced questions like this reveal whether a candidate has internalized CodeIgniter deeply enough to make architectural decisions. Strong answers demonstrate both breadth and depth of experience.
Answer
CI4's testing infrastructure allows mocking services to isolate units under test. The key method is Services::injectMock("email", $mockEmail) — after this call, any code that calls service("email") gets the mock instead. Use PHPUnit mocks: $mockEmail = $this->createMock(\CodeIgniter\Email\Email::class); $mockEmail->method("send")->willReturn(true); Services::injectMock("email", $mockEmail). Reset mocks after test: Services::reset(). For models: Factories::injectMock("models", "UserModel", $mockModel). For the database: use an in-memory SQLite database configured in app/Config/Database.php under the tests group. CI4's DatabaseTestTrait wraps each test in a transaction and rolls it back — faster than recreating the schema. Mock the Request with custom data: $this->request->setGlobal("post", ["name" => "Alice"]).
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