javascript - 如何使用 jest 测试 OOP JavaScript 服务

Question

所以我正在尝试为我所做的 JavaScript 服务编写一些测试。我有一项服务依赖于与该对象相关的变量 - 然后我使用这些变量来让一切正常工作。我遇到的问题是 this.playerState 在测试中是 undefined 吗？我想确保 this.playerStats.contentValue 等于 'test'。

const MyService = {
  init: function(context) {
    this.playerStats = {};
    this.checkForContextParam(context);
  },

  checkForContextParam: function(context) {
    if (context) {
      this.playerStats.contextValue = context
      this.playerStats.contextParam = 'context=' + this.playerStats.contextValue;
    } else {
      this.playerStats.contextValue = 'context_missing';
      this.playerStats.contextParam = 'error=' + this.playerStats.contextValue;
    }
  },
}

export default MyService;

这是我尝试运行的测试，但由于 this.playerStats 未定义而失败

test("Check for context param", () => {
  const context = {
    value: 'test',
  }
  this.playerStats = {}

  const result = MyService.checkForContextParam(context)
  expect(MyService.playerStats.contextValue).toEqual('test')
});

Answer 1

这是单元测试解决方案:

service.js:

const MyService = {
  init: function(context) {
    this.playerStats = {};
    this.checkForContextParam(context);
  },

  checkForContextParam: function(context) {
    if (context) {
      this.playerStats.contextValue = context;
      this.playerStats.contextParam = 'context=' + this.playerStats.contextValue;
    } else {
      this.playerStats.contextValue = 'context_missing';
      this.playerStats.contextParam = 'error=' + this.playerStats.contextValue;
    }
  },
};

export default MyService;

service.test.js:

import MyService from './service';

describe('MyService', () => {
  beforeEach(() => {
    const context = 'init';
    MyService.init(context);
  });
  describe('#checkForContextParam', () => {
    it('Check for context param', () => {
      const context = 'test';
      MyService.checkForContextParam(context);
      expect(MyService.playerStats.contextValue).toEqual(context);
      expect(MyService.playerStats.contextParam).toEqual('context=test');
    });

    it('context missing', () => {
      MyService.checkForContextParam();
      expect(MyService.playerStats.contextValue).toEqual('context_missing');
      expect(MyService.playerStats.contextParam).toEqual('error=context_missing');
    });
  });
});

带有覆盖率报告的单元测试结果:

 PASS  src/stackoverflow/59566126/service.test.js (8.133s)
  MyService
    #checkForContextParam
      ✓ Check for context param (5ms)
      ✓ context missing (1ms)

------------|----------|----------|----------|----------|-------------------|
File        |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
------------|----------|----------|----------|----------|-------------------|
All files   |      100 |      100 |      100 |      100 |                   |
 service.js |      100 |      100 |      100 |      100 |                   |
------------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests:       2 passed, 2 total
Snapshots:   0 total
Time:        9.338s

源代码:https://github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/59566126