茉莉花单元测试在所有测试中均失败，在单独运行时成功

Question

我有一个角度为8的项目，并且有一个现成的基本版本，“应该创建”单元测试失败，并出现错误“未捕获的TypeError：无法读取抛出的null的属性'forEach'”。问题在于，如果单独运行，此测试将成功，但是与该项目的所有其他单元测试一起运行时，该测试将失败。同样，在单元测试中创建的组件不包含任何forEach函数。

有问题的斑点

import { async, ComponentFixture, TestBed } from '@angular/core/testing';

import { SubheaderComponent } from './subheader.component';
import { requiredTestModules } from '../../testing/import.helpers';
import { ApplicationInsightsService } from '../../services/application-insight/app-insight.service';

describe('SubheaderComponent', () => {
  let component: SubheaderComponent;
  let fixture: ComponentFixture<SubheaderComponent>;

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [ SubheaderComponent ],
      imports: [
        requiredTestModules
      ],
      providers: [ApplicationInsightsService]
    })
    .compileComponents();
  }));

  beforeEach(() => {
    fixture = TestBed.createComponent(SubheaderComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

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

});

使用forEach代码未实现的其他组件：

component.ts

    console.log(selectedInvoices);
    this.selectedInvoices = selectedInvoices;
    let subtotal = 0;
    this.selectedInvoices.forEach((selectedInvoice) => {
    subtotal = +subtotal + +selectedInvoice.paymentAmt;
    });
    this.Subtotal =  subtotal;
    this.fee = this.feePercent / 100 * this.Subtotal;
    this.totalPayment = this.Subtotal + this.fee;
    console.log(this.selectedInvoices);

我确实有其他组件使用forEach，但是击中那些forEach（）的单元测试在隔离和全部运行方面均成功。

任何帮助/建议都将不胜感激。

Answer 1

看起来像是引起错误的forEach在组件测试之前被调用，而失败了。添加空检查使我的测试成功。

更新后的component.ts代码：

    if (this.selectedInvoices) {
      this.selectedInvoices = selectedInvoices;
      let subtotal = 0;
      this.selectedInvoices.forEach((selectedInvoice) => {
      subtotal = +subtotal + +selectedInvoice.paymentAmt;
      });
      this.Subtotal =  subtotal;
      this.convenienceFee = this.convenienceFeePercent / 100 * this.Subtotal;
      this.totalPayment = this.Subtotal + this.convenienceFee;
      console.log(this.selectedInvoices);
    }

如果错误是针对与存在错误不同的组件而引发的，则似乎很难进行调试，但这听起来像是更大的业障问题。感谢@Archit Garg的帮助。