What are the best practices for resetting mocks in Mockito

Understanding When to Use `reset()`

- Avoid Using `reset()`: The primary reason `reset()` exists is to support container-injected mocks, such as those used in legacy code or third-party interfaces. In most cases, especially with well-designed test-driven code, you should avoid using `reset()` and instead focus on creating small, focused test methods[2][4].

- Code Smell: If you find yourself needing to use `reset()` within a test method, it might be a sign that your tests are too complex or cover too many scenarios. This could indicate a need to refactor your tests or the code being tested[2].

Alternatives to `reset()`

- Create New Mocks: Instead of resetting mocks, consider creating new mock instances for each test method. This approach ensures that each test starts with a clean slate, reducing the risk of interactions from previous tests affecting the current one[4].

- Use `clearInvocations()`: If you only need to clear the invocation history (e.g., to verify interactions without affecting stubbing), use `Mockito.clearInvocations()`. This method removes invocation history without resetting stubs, which can be useful in certain scenarios[4].

Best Practices for Resetting Mocks

- Reset After Each Test: If you must reset mocks, do so after each test method using an `@After` annotation in JUnit or `afterEach()` in ScalaTest. This ensures that each test starts with a clean mock state[3][10].

- Avoid Resetting Before Tests: Resetting mocks before each test can lead to confusion about what state the mock is in at the start of the test. It's generally clearer to create new mocks or reset after tests[10].

- Use Framework Features: In frameworks like Spring, using annotations like `@MockBean` can automatically handle mock resetting after each test, eliminating the need for manual resets[10].

Conclusion

While Mockito provides the `reset()` method for specific use cases, it's generally advisable to avoid its use in favor of cleaner, more focused test design. By creating new mocks for each test or using framework features to manage mock state, you can ensure robust and maintainable tests without the need for manual resets.