Welcome to our lesson on using Fakes as test doubles in Test Driven Development (TDD) with Go and Testify. In this lesson, you'll explore how fakes can streamline your testing by simulating real-world components. Our journey so far has exposed you to various test doubles like dummies, stubs, and mocks. Now, we'll dive into fakes, which enable you to create realistic implementations that mirror complex dependencies, making your tests more robust and reliable. As always, we'll practice the TDD cycle: Red, Green, Refactor, as we see how fakes fit into our testing strategy.

Let's see how to implement a simple fake: an InMemoryUserRepository. This serves as a stand-in for a real database repository, providing controlled behavior for our tests.

Create a file in_memory_user_repository.go:

Explanation:

• We use a Go map to simulate an in-memory store for users.
• Each function mimics typical database operations such as creating and finding users.

Next, we will use the fake repository to test a UserService.

1. Red: Write Failing Tests

Create a test file user_service_test.go:

Run this test to confirm it fails, as we haven't implemented the logic yet.

1. Green: Implement Minimal Code

Now, create the user_service.go to ensure the test passes:

Rerun the test. It should now pass, confirming our implementation meets the defined requirement.

In this lesson, we explored the implementation and use of fakes in TDD, specifically via an in-memory repository for user management. Remember the steps of TDD:

• Red: Write a test that fails first, setting clear goals for implementation.
• Green: Implement just enough code to make your test pass.
• Refactor: Improve code quality without altering functionality.

Leverage the practice exercises to reinforce these concepts with hands-on examples. Congratulations on navigating the complexities of testing with fakes; your commitment is paving the way for building efficient, scalable applications. This is the final lesson of the course, so kudos for reaching this milestone! Keep exploring and applying TDD principles in your projects.