组件单元测试不只是在Angular 2 App中测试组件？

Question

I am trying to set up some unit tests in my Angular 2/AngularCLI app. While the app is working as expected, the testing shows failures.

So, to start simply (or so I thought), I set up a test component which I generated from the command line (ng gc testr). This creates a basic component test, along with the component files. When I CD into this component, and then run this built-in test with "ng test", I get errors related to other components in my app. This is confusing to me because I thought the individual component tests were unit tests - therefore, only designed to test that specific component. This is the example test for the component:

/* tslint:disable:no-unused-variable */
import { async, ComponentFixture, TestBed } from '@angular/core/testing';
import { By } from '@angular/platform-browser';
import { DebugElement } from '@angular/core';

import { TestrComponent } from './testr.component';

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

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [ TestrComponent ]
    })
    .compileComponents();
  }));

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

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

I assume this should be working "out of the box" - because it's set up automatically by the AngularCLI. So why the failure? Am I missing something here? Isn't the test code here designed to test the internal component, and not its relation to other components in the app?

Here's an example of one of the errors I'm getting. Clearly it's for a different component entirely. And I'm getting numerous errors like this for various components just from running this one test.

ERROR in ./src/app/app.component.ts
Module not found: Error: Can't resolve 'app/app.component.html' in '/Users/mko/Documents/abc-cli/abc-cli/cli-abc/src/app'
 @ ./src/app/app.component.ts 77:22-55
 @ ./src/app/app.component.spec.ts
 @ ./src \.spec\.ts
 @ ./src/test.ts

Here's another error pertaining again to a different component:

ERROR in ./src/app/views/client/client-panel.component.ts
Module not found: Error: Can't resolve 'app/views/client/client-panel.component.html' in '/Users/mko/Documents/abc-cli/abc-cli/cli-abc/src/app/views/client'
 @ ./src/app/views/client/client-panel.component.ts 34:22-88
 @ ./src/app/views/client/client-panel.component.spec.ts
 @ ./src \.spec\.ts
 @ ./src/test.ts

If I cd into a component and run "ng test", does or does that not run just the unit test for that component? And, if not, what do I need to change to make this just run the individual component test, and not all of them?

Answer 1

So I figured out the problem. Counter to what I assumed, out-of-the-box all individual component spec tests will run together because they are grouped together in a describe block. So cd'ing into a certain component and running "ng test" will NOT run just that test. It will in fact run ALL of them.

You can, however, run an individual component test by prefixing the describe function with something, like with f:

fdescribe('SomeComponent', () => {...}

If such a function exists, that will run, and no others.

But, more importantly, the takeaway here is that "ng test" is actually designed to run an entire SERIES of unit tests, not a single unit test.