effect.ts-testing

Mock services in Effect.ts tests by providing mock implementations using the built-in Layer system. This approach maintains type safety and ensures proper dependency injection, avoiding the test isolation issues caused by module-level mocks.

Module-level mocking tools like vi.mock() or jest.mock() break Effect.ts dependency injection because they replace entire modules, bypassing the Layer system. Effect requires services to be injected through Layers to correctly manage dependencies and isolate tests.

The best way to test HttpClient requests in Effect.ts is to provide a mock HttpClient Layer instead of mocking the platform module. This maintains type safety and correctly isolates the test environment using the built-in dependency injection system.

Test error cases and retry logic in Effect.ts by creating reusable mock Layer implementations that simulate failures. This allows you to verify that your code handles errors and retries correctly through the dependency injection system.

Yes, using Effect.ts Layers for mocking maintains TypeScript type checking for your mock implementations. This ensures that your mock services correctly match the interfaces of the real dependencies throughout your tests.