如何在角度 5 中对箭头函数进行单元测试

Question

这里是我需要测试的ts文件，Karma中未发现的代码只有下面一行

(value => {
      this.value = ++this.value;
    });

我是 Angular 新手，对单元测试完全陌生，请帮忙

import { Component, OnInit, Input, OnDestroy } from '@angular/core';
import { ToolHandlerService } from '../shared/services/toolhandler.service';
import { ISubscription } from 'rxjs/Subscription';

@Component({
  selector: 'basic-graphicresults',
  templateUrl: './graphicresults.component.html',
  styleUrls: ['./graphicresults.component.scss']
})
export class GraphicResultsComponent implements OnInit, OnDestroy {

  @Input() value: number;
  private replaceResultsSubscription: ISubscription;

  constructor(private toolHandlerService: ToolHandlerService) {
  }

  ngOnInit() {
    this.value=4;
    this.replaceResultsSubscription = this.toolHandlerService.onReplaceResults$.subscribe(value => {
      this.value = ++this.value;
    });
  }

  ngOnDestroy() {
    this.replaceResultsSubscription.unsubscribe();
  }
}

Answer 1

尝试在规范文件中创建一个 ToolHandlerService 类的模拟类，并将其注入到您的测试平台配置提供程序中，例如

providers: [{provide:ToolHandlerService, UseClass: MockToolHandlerService}]

然后在你的测试用例中这样做：

let isEventTriggered = false;
toolHandlerService.onReplaceResults$.subscribe(() => {
  isEventTriggered = true;
});
toolHandlerService.replaceResults.next();
expect(isEventTriggered).toBeTruthy();

通过执行上述操作，您将看到用例将被覆盖。

注意：这里使用的 ToolHandlerService 应该持有 MockToolHandlerService 的引用