javascript - Angular2单元测试选择下拉值

Question

我有一个县下拉列表。有一个默认值。用户可以选择一个国家。在更改时，它会将用户重定向到正确的国家/地区页面。哪个有效。

但是，我正在尝试对选择框中的默认值进行单元测试。但我不断将空字符串/值 selectEl.nativeElement.value 设为 ''。有人知道为什么吗？

// locale-component.ts
import { Component, OnInit } from '@angular/core';
import { Router, ActivatedRoute, Params } from '@angular/router';
import { cultures} from '../../../config/config';

@Component({
  selector: 'app-locale',
  templateUrl: './locale.component.html',
  styleUrls: ['./locale.component.scss']
})
export class LocaleComponent {

  cultures = cultures;

  constructor() {}

  onLocaleChange(locale) {
    const str = window.location.href.replace(new RegExp(`/${this.cultures.default}/`), `/${locale}/`);
    window.location.assign(str);
  }
}


  // locale.component.spec.ts

  beforeEach(() => {
    fixture = TestBed.createComponent(LocaleComponent);
    component = fixture.componentInstance;
    component.cultures = {
      default: 'en-ca',
      supported_cultures: [
        { "name": "United States", "code": "en-us" },
        { "name": "Canada (English)", "code": "en-ca" },
        { "name": "Canada (Français)", "code": "fr-ca" }
      ]
    }
    fixture.detectChanges();
  });

  it('should create', () => {
    expect(component).toBeTruthy();
  });

  it('should select the correct flag/locale by default', () => {
    fixture.detectChanges();
    const selectEl = fixture.debugElement.query(By.css('select'))
    console.log(selectEl)
    fixture.detectChanges();
    fixture.whenStable().then(() => {
      expect(selectEl.nativeElement.value).toEqual('en-ca');
    });

  });


<!-- locale.component.html -->

<label class="locale locale--footer">
  <div class="locale__custom-select locale__custom-select__button locale__custom-select__ff-hack">
    <select [ngModel]="cultures.default" (ngModelChange)="onLocaleChange($event)">
      <option *ngFor="let locale of cultures.supported_cultures" [ngValue]="locale.code">{{locale.name}}</option>
    </select>
  </div>
</label>

Answer 1

“在 whenStable() 内调用 detectChanges()”将填充下拉列表。

fixture.whenStable().then(() => {
  fixture.detectChanges();
  expect(selectEl.nativeElement.value).toEqual('en-ca');
});