使用mockResolvedValueOnce和async / await时抛出tslint警告

Question

I mocked request-promise module, everything is fine except tslint complains a warning.

Here is my unit test:

import * as request from 'request-promise';

jest.mock('request-promise', () => {
  return {
    __esModule: true,
    get: jest.fn(),
  };
});

describe('csv.service.ts', () => {
  it('should mock request-promise module correctly', () => {
    expect(jest.isMockFunction(request.get)).toBeTruthy();
  });
  it('should mock get method correctly', async () => {
    (request.get as jest.Mock).mockResolvedValueOnce('go?');
    const actualValue = await request.get('1');
    expect(actualValue).toBe('go?');
  });
});

Refactor this redundant 'await' on a non-promise. (no-invalid-await)tslint(1)

It seems that request.get('1') is not treat as a promise after executing mockResolvedValueOnce on request.get .

update

If I remove async/await , the second unit test will failed.

 FAIL  src/tests/services/core/csv.service.spec.ts
  csv.service.ts
    ✓ should mock request-promise module correctly (5ms)
    ✕ should mock get method correctly (9ms)

  ● csv.service.ts › should mock get method correctly

    expect(received).toBe(expected) // Object.is equality

    Expected: "go?"
    Received: {}

    Difference:

      Comparing two different types of values. Expected string but received object.

      17 | 
      18 |     const actualValue = request.get('1');
    > 19 |     expect(actualValue).toBe('go?');
         |                         ^
      20 |   });
      21 | });
      22 | 

      at Object.it (src/tests/services/core/csv.service.spec.ts:19:25)

Test Suites: 1 failed, 1 total
Tests:       1 failed, 1 passed, 2 total
Snapshots:   0 total
Time:        1.203s, estimated 2s

Answer 1

I use typecast to solve this issue. Because I am sure request.get('1') is a Promise after executing mockResolvedValueOnce on it.

const actualValue = await (request.get('1') as PromiseLike<string>);