在Jasmine中调用Angular Component方法后的初始值存储在变量中

如何解决在Jasmine中调用Angular Component方法后的初始值存储在变量中

我有一个组件如下：

// customer-reservation.component.ts
import {Component} from "@angular/core";

@Component({
  selector: 'app-customer-reservation',template: ``
})
export class CustomerReservationComponent {
  customerCount = 10;

  registerCustomer() {
    return this.customerCount++;
  }

  unregisterCustomer() {
    return this.customerCount--;
  }
}

以下是上述组件的规格文件：

// customer-reservation.component.spec.ts
import {ComponentFixture,Testbed} from "@angular/core/testing";
import { CustomerReservationComponent } from "./customerReservation.component";

describe('Room Reservation',() => {
  let fixture: ComponentFixture<CustomerReservationComponent>;
  let component: CustomerReservationComponent;
  beforeEach(() => {
    Testbed.configureTestingModule({
      declarations: [
        CustomerReservationComponent
      ]
    })

    // Set-up
    fixture = Testbed.createComponent(CustomerReservationComponent);
    component = fixture.componentInstance;

  })

  afterEach(() => {
    // Tear-down
    fixture = null;
    component = null;
  })

  it('Increase customer count in case of registration',() => {
    let customerCount: number;
    customerCount = component.registerCustomer();    // This is still 10
    expect(customerCount).toEqual(11);               // test fails

  })

  it('Decrease customer count in case of registration',() => {
    let customerCount: number;
    customerCount = component.unregisterCustomer(); // This is still 10
    expect(customerCount).toEqual(9);               // test fails
  })
})

我不明白为什么 customerCount 变量在这两种情况下的值为 10。它应该分别为规格存储 11 和 9 值。但是，当我用 customerCount 替换 component.customerCount 时，测试运行成功。有人可以帮助我为什么早期的方法没有更新本地 customerCount 变量与相应测试的递增和递减值。

解决方法

return this.customerCount++; 将始终在递增之前返回 this.customerCount 的值。

要使其与局部变量一起使用，您可以使用前缀递增/递减运算符：

  registerCustomer() {
    return ++this.customerCount;
  }

  unregisterCustomer() {
    return --this.customerCount;
  }