Angular 2 / 4 - 如何测试指令 @Input 值？答案

【问题标题】：Angular 2 / 4 - How to test Directive @Input values?Angular 2 / 4 - 如何测试指令 @Input 值？
【发布时间】：2017-12-30 07:59:03
【问题描述】：

所以我有一个需要输入的指令：

@Directive({
    selector: '[my-directive]'
})
export class MyDirective {

    @Input('some-input')
    public someInput: string;
}

如您所见，输入应该是string 值。现在，我想为这个指令写一个测试，我想测试输入是否满足string类型：

describe('MyDirective', () => {

    let fixture: ComponentFixture<DummyComponent>;
    let dummy: DummyComponent;
    let directive: DebugElement;

    beforeEach(async(() => {

        TestBed
            .configureTestingModule({
                imports: [
                    MyModule.forRoot()
                ],
                declarations: [
                    DummyComponent
                ]
            })
            .compileComponents();

        fixture = TestBed.createComponent(DummyComponent);
        dummy = fixture.componentInstance;
        directive = fixture.debugElement.query(By.directive(MyDirective));

        fixture.detectChanges();
    }));

    it('should satisfy only a string input and error on other inputs', () => {
        // How to test?
    });
});

@Component({
    selector: 'dummy',
    template: `
        <div my-directive [some-input]="'just-a-string-value'"></div>
    `
})
export class DummyComponent implements OnInit {
}

如何测试@Input 值是否属于正确类型？

【问题讨论】：

这个link 可能会有所帮助
directive 应该是 DebugElement[] ，要访问这个属性只需 typeof(directives[0].attributes.someInput).toLowerCase() == "string"

标签： angular unit-testing typescript testing jasmine

【解决方案1】：

所以有点晚了，但我来这里是为了寻找同样的问题，所以我会发布我的解决方案。这是我为测试指令输入（或其他属性）值所做的：

describe('MyDirective', () => {

    let fixture: ComponentFixture<DummyComponent>;
    let dummy: DummyComponent;
    let directive: DebugElement;

    beforeEach(async(() => {

        TestBed
            .configureTestingModule({
                imports: [
                    MyModule.forRoot()
                ],
                declarations: [
                    DummyComponent
                ]
            })
            .compileComponents();

        fixture = TestBed.createComponent(DummyComponent);
        dummy = fixture.componentInstance;
        directive = fixture.debugElement.query(By.directive(MyDirective));

        fixture.detectChanges();
    }));

    it('should satisfy only a string input and error on other inputs', () => {
        
        // needed so template is processed, inputs are updated
        fixture.detectChanges();
        
        // since we declared a ViewChild on the directive, we can access
        // and test directive properties values
        expect(component.directive.someInput).toEqual('just-a-string-value');
        // to test the input type :
        expect(component.directive.someInput).toEqual(Jasmine.any(String));
        // I thought TypeScript would complain when providing a wrong type input to a directive, but no...so I guess I'll test the input type too !
    });
});

@Component({
    selector: 'dummy',
    template: `
        <div my-directive [some-input]="'just-a-string-value'"></div>
    `
})
export class DummyComponent implements OnInit {

  // add a reference to the directive in template
  // so in your component you can access : this.directive, this.directive.someInput
  ViewChild(MyDirective) directive: MyDirective;
}

所以：修改您的测试组件以保存对指令实例的引用，然后通过 component.directive.[property-name] 访问指令属性。顺便说一句，如果您为指令属性提供默认值（可以通过在模板中提供值来覆盖），您可以在调用 fixture.detectChanges() 之前测试它们。

【讨论】：