node.js Jest 测试 exec.stdout.on(‘data’, data)

huangapple
go评论117阅读模式
英文:

nodejs Jest testing exec.stdout.on('data',data)

问题

尝试测试一个包含child_process库exec的函数。

  1. const { exec } = require('child_process')
  3. const randomFunc = () => { 
  4.   const newSync = exec('要执行的一些命令')
  5.   newSync.stdout.on('data', data => {
  6.    console.log(data.toString())
  7.   })
  8. }

testfile:

  1. const {randomFunc} = require(randomFuncFile)
  2. const { exec } = require('child_process')
  3. jest.mock('child_process')
  5. it('测试', () => {
  6.     const readStreamObject = {
  7.       on: jest.fn().mockImplementation(function (event, handler) {
  8.         handler('streaming ')
  9.       })
  10.     }
  11.    exec.mockImplementation(data => ({stdout: readStreamObject}))
  12.    randomFunc()
  13.    expect(exec.stdout.on).toHaveBeenCalled()
  14. }

我得到以下错误：

TypeError: Cannot read properties of undefined (reading 'on')

一些提示会很有帮助。

英文:

Trying to to test a function the incorporates the exec of child_process library.

  1. const { exec } = require('child_process')
  3. const randomFunc = () => { 
  4.   const newSync = exec('some command to execute')
  5.   newSync.stdout.on('data', data => {
  6.    console.log(data.toString())
  7.   })
  8. }

testfile:

  1. const {randomFunc} = require(randomFuncFile)
  2. const { exec } = require('child_process')
  3. jest.mock('child_process')
  5. it('test', () => {
  6.     const readStreamObject = {
  7.       on: jest.fn().mockImplementation(function (event, handler) {
  8.         handler('streaming ')
  9.       })
  10.     }
  11.    exec.mockImplementation(data => ({stdout: readStreamObject})
  12.    randomFunc()
  13.    expect(exec.stdout.on).toHaveBeenCalled()
  14. }

I'm getting

> TypeError: Cannot read properties of undefined (reading 'on')

some tips would be great.

答案1

得分: 1

你可以通过模拟的exec()函数获取模拟执行的stdout，方法是使用exec.mock.results[0].value.stdout，详见这里。

index.js：

  1. const { exec } = require('child_process');
  3. const randomFunc = () => {
  4.   const newSync = exec('要执行的某个命令');
  5.   newSync.stdout.on('data', (data) => {
  6.     console.log(data.toString());
  7.   });
  8. };
  10. module.exports = { randomFunc };

index.test.js：

  1. const { exec } = require('child_process');
  2. const { randomFunc } = require('./');
  4. jest.mock('child_process');
  6. it('测试', () => {
  7.   const mStdout = {
  8.     on: jest.fn().mockImplementation(function (event, handler) {
  9.       handler('流数据');
  10.     }),
  11.   };
  12.   exec.mockImplementation(() => ({ stdout: mStdout }));
  13.   randomFunc();
  14.   // expect(mStdout.on).toHaveBeenCalled();
  15.   // 或者
  16.   expect(exec.mock.results[0].value.stdout.on).toHaveBeenCalled();
  17. });

测试结果：

  1.  PASS  stackoverflow/75036469/index.test.js (8.403 s)
  2.   ✓ test (15 ms)
  4.   console.log
  5.     流数据
  7.       at stackoverflow/75036469/index.js:6:13
  9. ----------|---------|----------|---------|---------|-------------------
  10. File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
  11. ----------|---------|----------|---------|---------|-------------------
  12. All files |     100 |      100 |     100 |     100 |                   
  13.  index.js |     100 |      100 |     100 |     100 |                   
  14. ----------|---------|----------|---------|---------|-------------------
  15. Test Suites: 1 passed, 1 total
  16. Tests:       1 passed, 1 total
  17. Snapshots:   0 total
  18. Time:        9.016 s
英文:

You can get the mock stdout returned by mocked exec() function via exec.mock.results[0].value.stdout, See mockFn.mock.results

index.js:

  1. const { exec } = require('child_process');
  3. const randomFunc = () => {
  4.   const newSync = exec('some command to execute');
  5.   newSync.stdout.on('data', (data) => {
  6.     console.log(data.toString());
  7.   });
  8. };
  10. module.exports = { randomFunc };

index.test.js:

  1. const { exec } = require('child_process');
  2. const { randomFunc } = require('./');
  4. jest.mock('child_process');
  6. it('test', () => {
  7.   const mStdout = {
  8.     on: jest.fn().mockImplementation(function (event, handler) {
  9.       handler('streaming');
  10.     }),
  11.   };
  12.   exec.mockImplementation(() => ({ stdout: mStdout }));
  13.   randomFunc();
  14.   // expect(mStdout.on).toHaveBeenCalled();
  15.   // or
  16.   expect(exec.mock.results[0].value.stdout.on).toHaveBeenCalled();
  17. });

Test result:

  1.  PASS  stackoverflow/75036469/index.test.js (8.403 s)
  2.   ✓ test (15 ms)
  4.   console.log
  5.     streaming
  7.       at stackoverflow/75036469/index.js:6:13
  9. ----------|---------|----------|---------|---------|-------------------
  10. File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
  11. ----------|---------|----------|---------|---------|-------------------
  12. All files |     100 |      100 |     100 |     100 |                   
  13.  index.js |     100 |      100 |     100 |     100 |                   
  14. ----------|---------|----------|---------|---------|-------------------
  15. Test Suites: 1 passed, 1 total
  16. Tests:       1 passed, 1 total
  17. Snapshots:   0 total
  18. Time:        9.016 s

huangapple
  • 本文由 发表于 2023年1月7日 06:01:13
  • 转载请务必保留本文链接：https://go.coder-hub.com/75036469.html
  • javascript
  • jestjs
  • nested
  • node.js
  • unit-testing
匿名

发表评论

匿名网友

:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen:

确定