如何在异步componentDidMount axios调用中测试正确的状态更新？

Question

I have the following lifecycle with async/await

async componentDidMount() {
    try {
      const { name, key, expiration } = await DataService.getdata();
      this.setState({
        key,
        expiration,
        name,
      });
    } catch (err) {
      console.log(err);
    }
  }

I wrote the following test to test in state updated correctly when data comes from await call:

jest.mock("axios");

test('correct state update', () => {
      const responseText = {
        name: "test name",
        key: "test_key",
        expiration: null,
      };
      axios.get.mockResolvedValueOnce(responseText);
      const wrapper = shallow(<ComponentWrapper />);

      setImmediate(() => {
        expect(wrapper.state().name).toBe('test name');
        done();
      });
    });

But I have an error when the test runs:

      throw error;
      ^

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

Expected: "test name"
Received: undefined

Also, the test never ends, it continues to run

If I remove this test and just run test for correct rendering I have the following error:

TypeError: Cannot read property 'get' of undefined
 at Function.get (DataService.js:10:32)

Answer 1

Here is the solution:

index.ts :

import React, { Component } from 'react';
import { DataService } from './DataService';

interface ISomeComponentState {
  name: string;
  key: string;
  expiration: string | null;
}

export class SomeComponent extends Component<any, ISomeComponentState> {
  constructor(props) {
    super(props);
    this.state = {
      name: '',
      key: '',
      expiration: ''
    };
  }

  public async componentDidMount() {
    try {
      const { name, key, expiration } = await DataService.getdata();
      this.setState({ key, expiration, name });
    } catch (err) {
      console.log(err);
    }
  }

  public render() {
    const { name, key, expiration } = this.state;
    return (
      <div>
        key: {key}, name: {name}, expiration: {expiration}
      </div>
    );
  }
}

DataService.ts :

import axios from 'axios';

class DataService {
  public static async getdata() {
    return axios.get(`https://github.com/mrdulin`).then(() => {
      return {
        name: 'real name',
        key: 'real key',
        expiration: null
      };
    });
  }
}

export { DataService };

Unit test:

import React from 'react';
import { shallow } from 'enzyme';
import { SomeComponent } from './';
import { DataService } from './DataService';

jest.mock('./DataService.ts');

DataService.getdata = jest.fn();

describe('SomeComponent', () => {
  const responseText = {
    name: 'test name',
    key: 'test_key',
    expiration: null
  };
  it('correct state update', done => {
    (DataService.getdata as jest.MockedFunction<typeof DataService.getdata>).mockResolvedValueOnce(responseText);
    const wrapper = shallow(<SomeComponent></SomeComponent>);
    setImmediate(() => {
      expect(wrapper.state('name')).toBe(responseText.name);
      done();
    });
  });
});

Unit test result with coverage report:

 PASS  src/stackoverflow/56281185/index.spec.tsx (5.697s)
  SomeComponent
    ✓ correct state update (24ms)

----------------|----------|----------|----------|----------|-------------------|
File            |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
----------------|----------|----------|----------|----------|-------------------|
All files       |    88.46 |      100 |    71.43 |       85 |                   |
 DataService.ts |    71.43 |      100 |    33.33 |    71.43 |               5,6 |
 index.tsx      |    94.74 |      100 |      100 |    92.31 |                25 |
----------------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        6.582s

Here is the completed demo: https://github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/56281185