Angular 进行简单单元测试

前言

之前对单元测试的认知就是复杂，难搞，思路有，就是不知道怎样去实现，最近一次开会解决问题的过程中，发现原来单元测试可以十分简单，简单到几行代码就能实现。

示例

下面代码实现的功能是，判断课程所在的学院<College> college是否在用户所有的学院Array<College> colleges中，如果存在，变量show赋值为true，不存在，则赋值为false，如果college为undefined或者null，也赋值为true。

 /**
   * 观察课程学院是否与用户所在学院相同
   * @param college 课程学院
   * @param colleges 用户学院
   */
  public whetherShow(college: { id: number }, colleges: Array<{ id: number }>) {
    Assert.notNull(college, 'college未定义');
    const collegeId = college.id;
    let show = colleges != null && colleges && colleges.length > 0 ? false : true;
    if (colleges != null) {
      colleges.forEach(selectCollege => {
        if (collegeId === selectCollege.id) {
          show = true;
        }
      });
    }
    return show;
  }

要对该方法进行单元测试，思路就是传值进去进行对比，重点在于传值，用之前的思路就是，定义college和colleges,然后进行对比：

it('is show', () => {
    const college = new College({id: 1})
    const collegeOne  = new College({id: 1});
    const collegeTwo = new College({id: 2});
    component.colleges = [];
    expect(component.whetherShow(college,component.colleges)).toBe(true);
    component.colleges = undefined;
    expect(component.whetherShow(college,component.colleges)).toBe(true);
    component.colleges = [collegeOne];
    expect(component.whetherShow(college,component.colleges)).toBe(true);
    component.colleges = [collegeTwo];
    expect(component.whetherShow(college,component.colleges)).toBe(false);
    component.colleges = [collegeOne, collegeTwo];
    expect(component.whetherShow(college,component.colleges)).toBe(true);
  });

通过控制台的信息可以发现，无论是null还是undefined，都是可以通过的，后来老师提供了新的思路，既然要测试的是功能，就不要管怎么传的，可以不用传对象，然后就有了下面的写法：

  it('is show', () => {
    expect(component.whetherShow({id: 1}, null)).toBe(true);
    expect(component.whetherShow({id: 1}, undefined)).toBe(true);
    expect(component.whetherShow({id: 1}, [])).toBe(true);
    expect(component.whetherShow({id: 1}, [{id: 2}, {id: 3}])).toBe(false);
    expect(component.whetherShow({id: 1}, [{id: 1}, {id: 2}, {id: 3}])).toBe(true);
    expect(component.whetherShow({id: 1}, [{id: 2}, {id: 3}, {id: 1}])).toBe(true);
  });

值传进去了，方法也能判断了，比起之前的写法简直要好太多，而且对于一些方法来说，这种方法省力不少，尤其是对多种情况进行测试，要进行多个变量的定义：

 /**
   * 判断查询的关键字是否课程代码或名称中
   * @param course 课程
   * @param searchKey 查询关键字
   */
  public isCodeOrNameContainsSearchKey(course: { code: string, name: string }, searchKey: string) {
    return searchKey === null
      || course.code.toLowerCase().indexOf(searchKey.toLowerCase()) !== -1
      || course.name.toLowerCase().indexOf(searchKey.toLowerCase()) !== -1;
  }

该方法实现的是通过课程名称或代码进行查询操作，通过对查询关键字和课程名称或代码进行对比实现该功能，要考虑以下几种情况：查询关键字为null、查询关键字与课程名称或代码部分完全不相同、查询关键字与课程名称或代码部分相同、查询关键字与课程名称或代码完全相同、查询关键字包含课程名称或代码。
如果用旧思想进行测试：

 it('isCodeOrNameContainsSearchKey', () => {
    const courseOne = new Course({code: '', name: ''});
    const courseTwo = new Course({code: '222', name: ''});
    const courseThree = new Course({code: '', name: '222'});
    const courseFour = new Course({code: '222', name: '222'});
    expect(component.isCodeOrNameContainsSearchKey(courseOne, null));
    expect(component.isCodeOrNameContainsSearchKey(courseOne, ''));
    expect(component.isCodeOrNameContainsSearchKey(courseTwo, ''));
    expect(component.isCodeOrNameContainsSearchKey(courseTwo, '1111'));
    expect(component.isCodeOrNameContainsSearchKey(courseTwo, '22'));
    expect(component.isCodeOrNameContainsSearchKey(courseTwo, '222'));
    expect(component.isCodeOrNameContainsSearchKey(courseTwo, '2222'));
    expect(component.isCodeOrNameContainsSearchKey(courseThree, ''));
    expect(component.isCodeOrNameContainsSearchKey(courseThree, '1111'));
    expect(component.isCodeOrNameContainsSearchKey(courseThree, '22'));
    expect(component.isCodeOrNameContainsSearchKey(courseThree, '222'));
    expect(component.isCodeOrNameContainsSearchKey(courseThree, '2222'));
    expect(component.isCodeOrNameContainsSearchKey(courseFour, ''));
    expect(component.isCodeOrNameContainsSearchKey(courseFour, '1111'));
    expect(component.isCodeOrNameContainsSearchKey(courseFour, '22'));
    expect(component.isCodeOrNameContainsSearchKey(courseFour, '222'));
    expect(component.isCodeOrNameContainsSearchKey(courseFour, '2222'));
    
});

如果使用新思想：

  it('isCodeOrNameContainsSearchKey', () => {
    expect(component.isCodeOrNameContainsSearchKey({code: '', name: ''}, null)).toBe(true);
    expect(component.isCodeOrNameContainsSearchKey({code: '', name: ''}, '')).toBe(true);
    expect(component.isCodeOrNameContainsSearchKey({code: '222', name: ''}, '')).toBe(true);
    expect(component.isCodeOrNameContainsSearchKey({code: '222', name: ''}, '1111')).toBe(false);
    expect(component.isCodeOrNameContainsSearchKey({code: '222', name: ''}, '22')).toBe(true);
    expect(component.isCodeOrNameContainsSearchKey({code: '222', name: ''}, '222')).toBe(true);
    expect(component.isCodeOrNameContainsSearchKey({code: '222', name: ''}, '2222')).toBe(false);
    expect(component.isCodeOrNameContainsSearchKey({code: '', name: '222'}, '')).toBe(true);
    expect(component.isCodeOrNameContainsSearchKey({code: '', name: '222'}, '1111')).toBe(false);
    expect(component.isCodeOrNameContainsSearchKey({code: '', name: '222'}, '22')).toBe(true);
    expect(component.isCodeOrNameContainsSearchKey({code: '', name: '222'}, '222')).toBe(true);
    expect(component.isCodeOrNameContainsSearchKey({code: '', name: '222'}, '2222')).toBe(false);
    expect(component.isCodeOrNameContainsSearchKey({code: '222', name: '222'}, '')).toBe(true);
    expect(component.isCodeOrNameContainsSearchKey({code: '222', name: '222'}, '1111')).toBe(false);
    expect(component.isCodeOrNameContainsSearchKey({code: '222', name: '222'}, '22')).toBe(true);
    expect(component.isCodeOrNameContainsSearchKey({code: '222', name: '222'}, '222')).toBe(true);
    expect(component.isCodeOrNameContainsSearchKey({code: '222', name: '222'}, '2222')).toBe(false);
  });

设想一下自己看到他人写的测试代码，如果所需要的变量很少，courseOne等等能满足需求，看着也没问题，但是当变量很多的时候，估计写测试的都会忘记每个变量的属性值，更不用说看的人，而且，使用下面的方法写的代码，所需字段以及字段值一目了然，一行代码就能体现所有信息，看着也赏心悦目。

总结

简单的单元测试写起来真的要简单很多，而且感觉比之前的要优雅很多，看起来真的挺整洁的，整整齐齐的看着很舒服，感谢潘老师的指导，也感谢小伙伴们给予的帮助。

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本文作者：河北工业大学梦云智开发团队 张文达