Compare and contrast Sinon.js and Jest for mocking in a Node.js E2E testing environment.
Node.js interview question for Advanced practice.
Answer
Mocking external services in E2E tests is counterproductive when the goal is to test the interaction between the application and those external services. If we only mock the external services, the tests don't truly reflect the real-world behavior of the application. For example, mocking a payment gateway to always return a successful response would not reveal potential integration issues with the actual payment gateway. An alternative approach is to use a dedicated testing environment with real (but possibly stubbed) external services. This ensures that the tests are as close to a real-world scenario as possible, allowing for the detection of real integration issues. Using a testing environment with a test database and a non-production version of the external services would be a good approach.
Explanation
Mocking can be a powerful tool, but it can also lead to false positives in testing if not used judiciously.