在Jasmine中对MatDialog进行单元测试时，无法读取未定义的属性'afterClosed' [英] Cannot read property 'afterClosed' of undefined when unit testing MatDialog in Jasmine

问题描述

我从业力茉莉花中收到以下错误:
TypeError: Cannot read property 'afterClosed' of undefined

I get the following error from Karma Jasmine:
TypeError: Cannot read property 'afterClosed' of undefined

我进行了认真的搜索，但是在Stack Overflow或其他来源中找不到解决方案.

I searched sincerely, but I could not find a solution in Stack Overflow or in other sources.

这是我在组件中打开MatDialog的方式:
(就像记录)

This is how I open the MatDialog in my component:
(Like documented)

constructor(public dialog: MatDialog) {}

public openDialog(): void {
    const dialogReference: MatDialogRef<any, any> = this.dialog.open(myDialogComponent, {
        width: '1728px'
    });

    dialogReference.afterClosed().subscribe((result) => {
    });
}

这是我的单元测试配置:

This is my unit test config:

beforeEach(async(() => {
    TestBed.configureTestingModule({
        declarations: [
            myRequestComponent
        ],
        imports: [
            MatDialogModule,
            ReactiveFormsModule
        ],
        providers: [
            { provide: MatDialog, useValue: {} },
        ],
        schemas: [CUSTOM_ELEMENTS_SCHEMA]
    }).compileComponents();
}));

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

这是我的单元测试:

it('openDialog() should open a dialog', () => {
    spyOn(component.dialog, 'open');

    component.openDialog();

    expect(component.dialog.open).toHaveBeenCalled();
});

我必须模拟MatDialog或MatDialogReference吗?

Do I have to mock the MatDialog or the MatDialogReference?

推荐答案

让我们逐步解决您的问题.

Lets break your issue step by step.

第一，通过注册

providers: [{ provide: MatDialog, useValue: {} }],

每当需要解析MatDialog时，您的测试台将注入一个没有任何行为的对象(例如，实例方法/成员).

Your test bed will inject a an object with no behavior (eg. instance methods/members) whenever MatDialog needs to be resolved.

这不是真正必要的，因为您要将MatDialogModule导入到测试台中，因此可以解析MatDialog的实例而不会出现问题. 但是，请坚持使用您的方法.此解决方案将要求您删除该行.

This isn't truly necessary, as you are importing the MatDialogModule into your test bed, so an instance of MatDialog can be resolved without issues. But lets stick to your approach. This solution will require you to remove that line.

第二，方法是:

spyOn(component.dialog, 'open')

您要在component.dialog引用的对象中为open实例方法安装 proxy .在这种情况下，您先前注册的空对象.

you are installing a proxy for the open instance method in the object referenced by component.dialog. In this case, the empty object that you registered previously.

尽管该对象没有这样的成员，但是jasmine会在其位置动态添加代理.这就是为什么您没有看到类似this.dialog.open is not a function的错误的原因.

Despite the fact that the object does not have such a member, jasmine will dynamically add the proxy in its place. That is why you don´t see an error like this.dialog.open is not a function.

最后，只要与之交互，代理将记录有关这些交互的信息，并将呼叫重定向到原始的open成员.由于没有原始实现，因此一个没有返回值的函数将被替换在其位置，最终将触发accessing foo of undefined.

Lastly, whenever interacted with, the proxy will record information about those interactions and redirect the calls to the original open member. Because there was no original implementation, a function with no return will be used in its place, which will finally trigger the accessing foo of undefined.

TL; DR;

删除{ provide: MatDialog, useValue: {} }并使用以下命令模拟所需的MatDialogRef实例:

Remove { provide: MatDialog, useValue: {} } and use the following in order to mock the required MatDialogRef instance:

import { EMPTY} from 'rxjs';

it('openDialog() should open a dialog', () => {
    const openDialogSpy = spyOn(component.dialog, 'open')
        .and
        .returnValue({afterClosed: () => EMPTY});

    component.openDialog();

    expect(openDialogSpy).toHaveBeenCalled();
});

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