如何用值对 javascript 对象进行单元测试？

Question

我有一个 js 文件，我在其中读取一些值并将结果加载到一个变量中。我得到的好处是我不必每次需要时都从文件中读取。我可以简单地导入对象并使用它。

但是我不知道如何为它编写单元测试。

    const fs = require('fs');


const read_file = (path) => {
  try {
    const data = fs.readFileSync(path, 'utf8');
    return data;
  } catch (err) {
    console.error('Error in read_file', err);
    throw err;
  }
};

const getSecret = secretName => {
  try {
    return read_file(`/etc/secrets/${secretName}.txt`);
  } catch (err){
    throw err;
  }
};

const secretConfig = {
  kafka_keystore_password: getSecret('kafka_keystore_password')
};

module.exports = secretConfig;

我用jest写测试用例

我试过类似的方法，但对象仍然解析为未定义。

const secretConfig = require('./secret');
const fs = require('fs');
jest.mock('fs');
fs.readFileSync.mockReturnValue('randomPrivateKey');


 

describe('secret read files', () => {
    
  it('should read secret from file', async () => {
    const secretMessage = secretConfig.kafka_keystore_password;
    expect(secretMessage).toEqual('randomPrivateKey');

  })

})

secret read files › should read secret from file

expect(received).toEqual(expected) // deep equality

Expected: "randomPrivateKey"
Received: undefined

  18 |     const secretMessage = secretConfig.kafka_keystore_password;
  19 |     //expect(fs.readFileSync).toHaveBeenCalled();
> 20 |     expect(secretMessage).toEqual('randomPrivateKey');

Answer 1

你的测试是正确的。问题是您需要在 require 之前模拟 ./secret 模块，因为 getSecret 方法将在需要模块时立即执行。此时，fs.readFileSync 还没有被赋予模拟值。

const fs = require('fs');
fs.readFileSync.mockReturnValue('randomPrivateKey');
const secretConfig = require('./secret');

jest.mock('fs');

describe('secret read files', () => {
  it('should read secret from file', async () => {
    const secretMessage = secretConfig.kafka_keystore_password;
    expect(secretMessage).toEqual('randomPrivateKey');
  });
});

测试结果：

> jest "-o" "--coverage"

 PASS  examples/69283738/secret.test.js (7.265 s)
  secret read files
    ✓ should read secret from file (2 ms)

-----------|---------|----------|---------|---------|-------------------
File       | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
-----------|---------|----------|---------|---------|-------------------
All files  |   76.92 |      100 |     100 |   76.92 |                   
 secret.js |   76.92 |      100 |     100 |   76.92 | 8-9,17            
-----------|---------|----------|---------|---------|-------------------
Test Suites: 1 passed, 1 total
Tests:       1 passed, 1 total
Snapshots:   0 total
Time:        7.794 s

如何用值对 javascript 对象进行单元测试？

How to unit test a javascript object with value?

javascript

unit-testing

jestjs

fs

ts-jest