Question

我正在编写单元测试，并在包'child_process'中模拟'exec'方法。

__嘲笑__ / child_process.js

const child_process = jest.genMockFromModule('child_process');
child_process.exec = jest.fn()

module.exports = child_process;

这是测试文件：

const fs = require('fs-extra'),
      child_process = require('child_process'),
      runCassandraMigration = require('../../lib/runCassandraMigration.js')

const defaultArguments = () => {
  return {
    migration_script_path: './home',
    logger: {
      error: function () {}
    }
  };
}

jest.mock("fs-extra")
jest.mock("child_process")

describe('Running cassandra migration tests', function () {
  describe('successful flow', function () {
    it('Should pass without any errors ', async function () {
        let args = defaultArguments();
        let loggerSpy = jest.spyOn(args.logger, 'error')

        fs.remove.mockImplementation(() => {Promise.resolve()})
        child_process.exec.mockImplementation(() => {Promise.resolve()})

        await runCassandraMigration(args.migration_script_path, args.logger)
    });
  });

当我运行测试时，我收到以下错误：

child_process.exec.mockImplementation is not a function

我测试的模块

const fs = require('fs-extra')
const promisify = require('util').promisify
const execAsync = promisify(require('child_process').exec)

module.exports = async (migration_script_path, logger) => {
  try {
    console.log()
    const {stdout, stderr} = await execAsync(`cassandra-migration ${migration_script_path}`)
    logger.info({stdout: stdout, stderr: stderr}, 'Finished runing cassandra migration')
    await fs.remove(migration_script_path)
  } catch (e) {
    logger.error(e, 'Failed to run cassandra migration')
    throw Error()
  }
}

请告知。

Answer 1

迟到... answer ？...

昨天我遇到了同样的错误，问题是我没有在测试文件中调用jest.mock('child_process')。

笑话documentation说，当嘲笑Node的核心模块调用jest.mock('child_process') is required时。我看到您这样做了，但由于某种原因它无法正常工作（也许Jest没有将其提升到顶部）。

无论如何，在Jest版本24.9.0中，我没有遇到child_process.exec.mockImplementation is not a function错误，但是由于您的测试没有很好地实现，所以出现了一些其他错误。

为使您的测试正常进行，我：

在info: function () {},内添加了logger

将exec的实现更新为child_process.exec.mockImplementation((command, callback) => callback(null, {stdout: 'ok'})) 并且（对于通过测试不是必须的）将fs.remove的实现更新为fs.remove.mockImplementation(() => Promise.resolve())

赞：

const fs = require('fs-extra'),
      child_process = require('child_process'),
      runCassandraMigration = require('./stack')

const defaultArguments = () => {
  return {
    migration_script_path: './home',
    logger: {
      info: function () {},
      error: function () {}
    }
  };
}

jest.mock("fs-extra")
jest.mock("child_process")

describe('Running cassandra migration tests', function () {
  describe('successful flow', function () {
    it('Should pass without any errors ', async function () {
        let args = defaultArguments();
        let loggerSpy = jest.spyOn(args.logger, 'error')

        fs.remove.mockImplementation(() => Promise.resolve())
        child_process.exec.mockImplementation((command, callback) => callback(null, {stdout: 'ok'}))

        await runCassandraMigration(args.migration_script_path, args.logger)
    });
  });
});

Jest - 'child_process'包中的mock函数

1 个答案: