angular - Angular 6+单元测试中的spyOn isDevMode()？

Question

我的代码包括 if像这样阻止

服务:

import { isDevMode } from '@angular/core';

export class MyService {
  constructor() {}

  methodToTest(): {
    if (!isDevMode()) {
      doSomething();
    } else {
      doSomethingDifferentInDevMode();
    }
  }
}

my-service.spec.ts(仅相关行):

it('should run doSomething() when isDevMode() returns false', () => {
  // what should i do here to mock a false value return for isDevMode() ?
  expect(doSomething).toHaveBeenCalled();
});

我如何监视 isDevMode()让它为这个单一的 Angular 单元测试返回 false，以便我可以测试 doSomething()叫做？

Answer 1

首先将此函数包装到服务中:

import { isDevMode, Injectable } from '@angular/core';

@Injectable({ providedIn: 'root' })
export class DevModeService {
  constructor() {}

  isDevMode() {
    return isDevMode();
  }
}

然后你可以在任何你想要的地方注入(inject)这个服务，就像你对任何其他服务所做的那样:

import { DevModeService } from 'dev-mode.service';

export class MyService {
  constructor(private devModeService: DevModeService) {}

  methodToTest(): {
    if (!this.devModeService.isDevMode()) {
      doSomething();
    } else {
      doSomethingElse();
    }
  }
}

然后，您可以在测试 MyService 时监视 DevModeService，就像您对任何其他依赖项所做的那样:

it('should do something when in dev mode') {
  const devModeService = TestBed.inject(DevModeService);
  spyOn(devModeService, 'isDevMode').and.returnValue(true);

  const myService = TestBed.inject(MyService);
  myService.methodToTest();
  // ...
}

it('should do something else when in prod mode') {
  const devModeService = TestBed.inject(DevModeService);
  spyOn(devModeService, 'isDevMode').and.returnValue(false);

  const myService = TestBed.inject(MyService);
  myService.methodToTest();
  // ...
}