picking-test-doubles

Choose fake vs mock based on dependency state and interaction needs. Fakes are ideal for state-bearing dependencies to keep tests maintainable, while mocks verify specific interactions without coupling to implementation details.

To stop Mockito from making Android tests brittle, shift to fakes for state-bearing dependencies. Fakes avoid tight coupling to implementation details, ensuring tests remain reliable and maintainable across refactors.

The best way to structure Android test doubles for ViewModel tests is using custom fakes for repositories. This approach enforces a lightweight, maintainable hierarchy by validating test design against established Google preferences.

Robolectric shadows can be used for framework-level substitutions in Android integration tests. They provide specialized environment handling where fakes or mocks are insufficient for validating actual device behavior.

Over-mocking leads to brittle Android unit tests because it forces tests to focus on implementation details rather than actual behavior. This tight coupling causes tests to break unnecessarily during code refactoring.

Dependency injection is required to effectively use test doubles in Android testing. Injecting dependencies allows you to seamlessly substitute real components with fakes or mocks during unit and integration testing scenarios.