单元测试有问题 angular 从按钮点击重置响应式表单控件

Question

我在为我的 angular 应用程序编写 jasmine 单元测试用例时遇到问题。有一个反应形式，并试图通过单击按钮重置特定的表单控件。尽管场景应该足够简单以供测试，但我似乎在这里遗漏了一些东西。

下面是应用程序的代码片段。

app.component.html:

<form [formGroup]="userForm" novalidate (ngSubmit)="onSubmit()">
  <div>
    <input
      type="text"
      id="fNameFld"
      name="fName"
      formControlName="fName"
      placeholder="First Name"
    />
    <button (click)="clearField('fName')" id="clrFName">
      Clear First Name
    </button>
  </div>

  <div>
    <input
      type="text"
      id="lNameFld"
      name="lName"
      formControlName="lName"
      placeholder="Last Name"
    />
    <button (click)="clearField('lName')" id="clrLName">Clear Last Name</button>
  </div>

  <div>
    <button type="submit">Submit</button>
  </div>
</form>

app.component.ts

import { FormBuilder, FormGroup } from '@angular/forms';

@Component({
  selector: 'my-app',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css'],
})
export class AppComponent implements OnInit {
  name = 'Angular ' + VERSION.major;
  userForm: FormGroup;

  constructor(private readonly fb: FormBuilder) {}

  ngOnInit() {
    this.userForm = this.fb.group({
      fName: this.fb.control(null),
      lName: this.fb.control(null),
    });
  }

  onSubmit() {
    console.log('Submitted Data', this.userForm.value);
  }

  clearField(controlName: string) {
    this.userForm.get(controlName).reset();
  }
}

单元测试代码

it('should clear fName control when the "Clear First Name" button is clicked', () => { 
    const spy = spyOn(component, 'clearField');
    const clearBtn = fixture.debugElement.query(By.css("button#clrFName"));
    const form = component.userForm;
    
    form.patchValue({
      'fName': 'John,
      'lName': 'Doe'
    });
    
    clearBtn.nativeElement.click();
    fixture.detectChanges();
    expect(spy).toHaveBeenCalledTimes(1);  // passes
    expect(spy).toHaveBeenCalledWith('fName');  // passes
    expect(form.get('fName').value).toBeNull();  // fails: Expected 'John' to be null.
  });

Angular: 10.0.14

Angular CLI：10.0.8

StackBlitz：https://angular-ivy-fc6rik.stackblitz.io

Answer 1

你好像在嘲笑 clearField。添加此内容以在您模拟它时实际执行其内容：

const spy = spyOn(component, 'clearField').and.callThrough();

所以每次 clearField 被调用时，它都会触发间谍（所以你知道它是否被调用），并会执行它的内容。

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