角4茉莉间谍单元测试“预计未定义为'新文本'

Question

我有一个简单的函数修改我的app.component.ts中的参数，我想用间谍测试函数。我的changeText函数总是未定义出于某种原因，我在做什么错？

AppComponent.ts

export class AppComponent { 
    text = "My text"; 

    changeText = function() { 
     this.text = "New text"; 
     return this.text; 
    } 
} 

AppComponent.spec.ts

describe("my text with Spies", function() { 
     it("should be altered", function() { 
     const fixture = TestBed.createComponent(AppComponent); 
     const app = this.fixture.debugElement.componentInstance; 

     spyOn(app, 'changeText'); 

     expect(app.text).toBe("My text")  
     expect(app.changeText()).toBe("New text");   //Fails 
     expect(app.changeText).toHaveBeenCalledTimes(1); 
    }); 
}); 

Answer 1

尝试添加这种改变如果这实际上仍然

更改此：

expect(app.changeText()).toBe("New text"); 
expect(app.changeText).toHaveBeenCalledTimes(1); 

到：

app.changeText(); 
expect(app.text).toBe("New text"); 
expect(app.changeText).toHaveBeenCalled();