When it comes to end to end testing, one of the biggest decisions teams face is whether to mock external services or test against real ones. Both approaches have their advantages, and choosing the right one often depends on the stage of development, the complexity of the system, and how much reliability you need from your test suite.
Mocking is generally the easier and faster route. By simulating external APIs, databases, or third-party integrations, you get tests that run consistently and avoid network-related issues. This is especially helpful during early development, where real services might still be unstable or incomplete. Mocks also give you full control over responses, which makes it easier to test edge cases and error-handling scenarios. The downside? Mocks can drift away from real behavior, causing tests to pass even when production would fail.
On the other hand, using real services in end to end testing provides a true representation of how your application behaves in real-world conditions. This approach catches integration issues that mocks simply can’t replicate—things like authentication flows, performance bottlenecks, or subtle data inconsistencies. Of course, the trade-off is that tests can become slower, more brittle, and harder to maintain due to dependencies on external systems.
A balanced strategy often works best. Many teams mock services for daily CI test runs and reserve real-service tests for nightly or pre-release pipelines. Tools like Keploy can also help by capturing real traffic and generating consistent test cases and mocks, reducing the manual effort of maintaining both types of tests.
Ultimately, the key is understanding your goals. Mocking gives speed and stability, while real services give accuracy and confidence. The most effective testing pipelines combine both, ensuring that your application remains reliable without slowing down your development workflow.