redux-saga测试while( true ) -使saga.next().done为true

Question

我正在测试一个民调传奇。

export function* sagaWithPolling() {
  while (true) {
    try {
      // saga body
    } catch (error) {
      yield put(stopPolling());
      yield put(displayError(error));
    }
  }
}

测试：

 describe('error flow', () => {
    const saga = sagaWithPolling();

    saga.next();

    test('stop polling', () => {
      const actual = saga.throw(TEST_ERROR).value;
      const expected = put(stopPolling());

      expect(actual).toEqual(expected);
    });

    test('should display error', () => {
      const actual = saga.next().value;
      const expected = put(displayError(TEST_ERROR));

      expect(actual).toEqual(expected);
    });

    test('be done', () => {
      const actual = saga.next().done;
      const expected = true;

      expect(actual).toEqual(expected);
    });
  });

这个测试对于一般的传奇来说是通过的，但是对于轮询和使用while(true)的测试，它在最后一步失败了，因为saga.next().done是false，因为它继续轮询。你知道如何指出它停止了轮询吗？

Answer 1

由于在生成器中定义了无限循环，gen.next()将让生成器在该无限循环(try块)中无限取值。该值始终为{value: 1, done: false}。生成器将永远不会结束。

您应该使用Generator.prototype.return()返回给定值并完成生成器。

例如。

saga.ts

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

export function stopPolling() {
  return { type: 'STOP_POLLING' };
}
export function displayError(error) {
  return { type: 'DISPLAY_ERROR', payload: error };
}

export function* sagaWithPolling() {
  while (true) {
    try {
      // saga body
      yield 1;
    } catch (error) {
      yield put(stopPolling());
      yield put(displayError(error));
    }
  }
}

saga.test.ts

import { put } from 'redux-saga/effects';
import { displayError, sagaWithPolling, stopPolling } from '.';

describe('error flow', () => {
  const saga = sagaWithPolling();
  const TEST_ERROR = new Error('network');

  saga.next();

  test('stop polling', () => {
    const actual = saga.throw(TEST_ERROR).value;
    const expected = put(stopPolling());
    expect(actual).toEqual(expected);
  });

  test('should display error', () => {
    const actual = saga.next().value;
    const expected = put(displayError(TEST_ERROR));
    expect(actual).toEqual(expected);
  });

  test('be done', () => {
    const actual = saga.return().done;
    const expected = true;
    expect(actual).toEqual(expected);
  });
});

测试结果：

 PASS  src/stackoverflow/65237271/index.test.ts
  error flow
    ✓ stop polling (3 ms)
    ✓ should display error (1 ms)
    ✓ be done

Test Suites: 1 passed, 1 total
Tests:       3 passed, 3 total
Snapshots:   0 total
Time:        2.067 s, estimated 3 s