Effect CommunityEC
Effect Community•4mo ago
nemmtor

Overriding a Single Method in `Path` for Testing Without Type Casting

I wanna override a single method of 
Path
 in tests, is there easier way to achieve it without type casting?

I tried to do it via Effect.provideService but it requires full implementation of 
Path
 so had to type cast. Also tried Layer.mock but found it only works for effects where 
Path
 is not effectful.

describe('program', () => {
  it('calls path.join', async () => {
    const join = mock();
    const layer = createTestPathLayer({ join });
    await program.pipe(Effect.provide(layer), Effect.runPromise);

    expect(join).toHaveBeenCalled();
  });
});

const createTestPathLayer = (overrides?: Partial<Path.Path>) =>
  Layer.effect(
    Path.Path,
    Effect.gen(function* () {
      const path = yield* Path.Path;

      return { ...path, ...overrides };
    }).pipe(Effect.provide(Path.layer)),
  );
Was this page helpful?