angular - 是什么导致 "Cannot configure the test module when the test module has already been instantiated"？

Question

这是我的测试:

describe('ValueService', () => {

  it('#getValue should return real value', () => {
    expect(true).toBeTruthy();
   });
});

我有这个错误:

Failed: Cannot configure the test module when the test module has already been instantiated. Make sure you are not using inject before R3TestBed.configureTestingModule.Error: Cannot configure the test module when the test module has already been instantiated. Make sure you are not using inject before R3TestBed.configureTestingModule.

Answer 1

正如与作者讨论的那样，问题出现在 TestBed 时在 describe 之外初始化当有两个或更多规范文件时。
例如:

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [
        RouterTestingModule
      ],
      declarations: [
        AppComponent
      ],
    }).compileComponents();
  }));
describe('AppComponent', () => {
  it('should create the app', () => {
    const fixture = TestBed.createComponent(AppComponent);
    const app = fixture.componentInstance;
    expect(app).toBeTruthy();
  });
 });

将实例化 TestBed beforeEach 测试，不仅是规范文件。因此，如果您有另一个带有 TestBed 和 beforeEach 的 .spec，它将被解释为 2 个 TestBed，如下所示:

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [
        RouterTestingModule
      ],
      declarations: [
        AppComponent
      ],
    }).compileComponents();
  }));
  beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [
        RouterTestingModule
      ],
      declarations: [
        AppComponent
      ],
    }).compileComponents();
  }));
describe('AppComponent', () => {
  it('should create the app', () => {
    const fixture = TestBed.createComponent(AppComponent);
    const app = fixture.componentInstance;
    expect(app).toBeTruthy();
  });
 });

错误

Failed: Cannot configure the test module when the test module hasalready been instantiated.

会是对的，因为您实例化了两个 TestBed(但在两个规范文件中)。
要解决此问题，您必须始终放置 TestBed定义(所以 beforeEach )在这样的描述中:

describe('AppComponent', () => {
  beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [
        RouterTestingModule
      ],
      declarations: [
        AppComponent
      ],
    }).compileComponents();
  }));

  it('should create the app', () => {
    const fixture = TestBed.createComponent(AppComponent);
    const app = fixture.componentInstance;
    expect(app).toBeTruthy();
  });
});