When should you mock the API, and when not?

#When to mock the API

• when the backend is unstable, unavailable or not ready yet
• when guaranteed, repeatable data behavior is needed
• when it is important to check rare cases (500 errors, empty responses, timeouts)
• when tests need to be fast and not depend on the network
• when it comes to local development or CI, where predictability matters

#When NOT to mock the API

• when you need to make sure the real frontend → backend connection works end-to-end
• when the test checks a real user scenario, not just the UI
• when it is important to test integration, not an isolated interface
• when you need to catch a regression in the real service, not in fake data

Summary in one line: We mock for stability and speed. We don't mock when we are checking reality, not an imitation.