您应该使用task.toPromise()将runSaga()返回的任务转换为承诺，请参阅任务。然后使用async/await等待任务完成。
例如
saga.ts：

import { put } from 'redux-saga/effects';

const ApiEndpoint = 'http://localhost:3000';
const INVALID_PAGE_LOAD = 'INVALID_PAGE_LOAD';
export const getReleaseCommitsSuccess = (payload) => ({ type: 'GET_RELEASE_COMMITS_SUCCESS', payload });
export const getReleaseCommitsFailure = (payload) => ({ type: 'GET_RELEASE_COMMITS_FAILURE', payload });

export function* releaseCommitsSaga({ release, product }) {
  if (release && product) {
    const response = yield fetch(`${ApiEndpoint}/ReleaseCommits?product=${product}&version=${release}`);

    const releaseCommits = yield response.json().catch((error) => error);

    if (response.status === 200) {
      console.log(releaseCommits);
      yield put(getReleaseCommitsSuccess(releaseCommits));
    } else {
      yield put(getReleaseCommitsFailure('release commits could not be fetched'));
    }
  } else {
    yield put({
      type: INVALID_PAGE_LOAD,
    });
  }
}

saga.test.ts：

import { Action } from 'redux';
import { runSaga } from 'redux-saga';
import { releaseCommitsSaga } from './saga';

describe('74999487', () => {
  it('releaseCommitsSaga success', async () => {
    const response = [
      {
        package: 'package_abc',
        id: 'long_id',
        committer: 'someone@something.com',
        message: 'commit msg',
      },
    ];
    (global as any).fetch = jest.fn(() =>
      Promise.resolve({
        status: 200,
        json: () => Promise.resolve(response),
      }),
    );
    const dispatched: Action[] = [];
    await runSaga(
      {
        dispatch: (action: Action) => {
          console.log(action);
          dispatched.push(action);
        },
      },
      releaseCommitsSaga,
      { product: 'a', release: 'v1' },
    ).toPromise();

    expect(fetch).toHaveBeenCalled();
    expect(dispatched).toEqual([{ type: 'GET_RELEASE_COMMITS_SUCCESS', payload: response }]);
    (global.fetch as jest.MockedFunction<typeof fetch>).mockClear();
  });
});

试验结果：

PASS   redux-saga-examples  packages/redux-saga-examples/src/stackoverflow/74999487/saga.test.ts
  74999487
    ✓ releaseCommitsSaga success (23 ms)

  console.log
    [
      {
        package: 'package_abc',
        id: 'long_id',
        committer: 'someone@something.com',
        message: 'commit msg'
      }
    ]

      at packages/redux-saga-examples/src/stackoverflow/74999487/saga.ts:15:15

  console.log
    {
      type: 'GET_RELEASE_COMMITS_SUCCESS',
      payload: [
        {
          package: 'package_abc',
          id: 'long_id',
          committer: 'someone@something.com',
          message: 'commit msg'
        }
      ]
    }

      at dispatch (packages/redux-saga-examples/src/stackoverflow/74999487/saga.test.ts:25:19)

----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
----------|---------|----------|---------|---------|-------------------
All files |   82.61 |       50 |      50 |   85.71 |                   
 saga.ts  |   82.61 |       50 |      50 |   85.71 | 18-21             
----------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        3.142 s

软件包版本：

"redux": "^4.1.0",
"redux-saga": "^1.1.3",