Typescript types do not include returned values, important object attributes

[EButlerIV]

mockResponse, mockResponseOnce, etc. do not return void

According to index.d.ts, mockResponse, etc all return void.

mockResponse(body: string, init?: MockParams): void;
mockResponseOnce(body: string, init?: MockParams): void;
mockResponses(responses: Array<{body: string, init?: MockParams}>): void;

In actuality, they all return the mocked fetch fn., so we can chain mockResponse calls.

fetch.mock isn't included in the definition

Since mock isn't included in the definition and the fetch definition doesn't extend jest's mocked function definition, uses of .mock.calls fail type checking.

[jefflau]

Would you have time to help write that definition? I am not a typescript developer but would welcome pull requests for it

[EButlerIV]

Sure. I'll submit a PR within the next few days.

[jefflau]

Thanks!

[caseyduquettesc]

For anyone looking for a temporary solution, they can alter the type globally, but in the test files, they'll need to refer to fetch using global.fetch instead. It's just a workaround for anyone being blocked.

// custom.jest.d.ts
import mockFetch from 'jest-fetch-mock';

declare global {
  namespace NodeJS {
    interface Global {
      fetch: JFM;
    }
  }
  type JFM1 = typeof mockFetch;
  export interface JFM extends JFM1, jest.MockInstance<any> {}
}

// setupJest.ts
import mockFetch from 'jest-fetch-mock';

global.fetch = (mockFetch as JFM);

// __tests__/demo.test.ts

it('works', () => {
  global.fetch.resetMocks();
  global.fetch.mockResponseOnce('');
  // fetch()
  expect(global.fetch.mock.calls.length).toEqual(1);
});

[ravenscar]

@EButlerIV looking at the docs for mockResponses I think the type signature is wrong. This isn't something you introduced I think it has always been wrong, I think it should be:

mockResponses(...responses : Array<[string] | [string, MockParams]>) : Fetch;

not

mockResponses(responses: Array<{body: string, init?: MockParams}>): Fetch;

What do you think?

[billreed63]

This fix would be really helpful for me, do we have a ETA on when it will be merged? Thanks!

[EButlerIV]

Oh, sorry. I didn't see any of the subsequent conversation. @ravenscar is correct.