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[英]Angular 7: ngOnInit() of the a component is getting called every time running unit test case of that component
[英]Angular 2 unit test function called from ngOnInit
我正在尝试对组件内的一个函数进行单元测试,这个函数是根据一个初始条件从ngOnInit调用的:
ngOnInit() {
if (this.list.length === 0) {
return this.loadData();
}
return this.isLoading = false;
}
// I'm calling here because it could also be called from button on the UI
loadData() {
this.apiService.apiGet().subscribe((response) => {
// handle data
return this.isLoading = false;
}, (error) => {
// handle error
return this.isLoading = false;
})
}
但除非我在测试中手动调用该函数,否则我无法测试它。 这是我的测试代码:
// THIS CODE WORKS
it('should be false after calling loadData()', async(() => {
component.loadData();
fixture.detectChanges();
fixture.whenStable().then(() => {
expect(component.isLoading).toBeFalsy();
});
}));
// THIS CODE DOESN'T work
it('should be false after calling loadData()', async(() => {
spyOn(component,'loadData').and.returnValue({code:'success'});
fixture.detectChanges();
fixture.whenStable().then(() => {
expect(component.isLoading).toBeFalsy();
});
}));
这也是我用来模拟apiGet函数的一段代码:
apiGet() {
return Observable.of({ data: 'success' });
}
但是我知道正在执行ngOnInit并且正在调用该函数,因为此测试通过:
it('should be called if list array is empty', () => {
spyOn(component,'loadData').and.returnValue({code:'success'});
fixture.detectChanges();
expect(component.loadData).toHaveBeenCalled();
});
我究竟做错了什么? 为什么测试费用没有达到最终的承诺?
这个isLoading
方法没有设置isLoading
,而它返回一个与此无关的值:
spyOn(component,'loadData').and.returnValue({code:'success'});
所以它的行为明显不同于真正的方法。 如果这意味着这使得这个期望是错误的,那就是它:
expect(component.isLoading).toBeFalsy();
测试这个的正确方法是逐行测试几个隔离的规范:
// ngOnInit test
spyOn(component, 'loadData');
this.list.length = 0;
fixture.detectChanges();
expect(component.loadData).toHaveBeenCalled();
expect(component.isLoading).toBe(true);
// ngOnInit test
spyOn(component, 'loadData');
this.list.length = 1;
fixture.detectChanges();
expect(component.loadData).not.toHaveBeenCalled();
expect(component.isLoading).toBe(false);
// loadData test
const apiServiceMock = {
apiGet: jasmine.createSpy().and.returnValue(Observable.of(...))
};
this.apiService = apiServiceMock; // or mock via DI
spyOn(component, 'loadData').andCallThrough();
fixture.detectChanges();
// OR
// component.loadData()
expect(component.loadData).toHaveBeenCalled();
expect(apiServiceMock.apiGet).toHaveBeenCalled()
expect(component.isLoading).toBe(false);
// loadData test
const apiServiceMock = {
apiGet: jasmine.createSpy().and.returnValue(Observable.throw(...))
};
// the rest is same
// loadData test
const apiServiceMock = {
apiGet: jasmine.createSpy().and.returnValue(Observable.empty())
};
fixture.detectChanges();
expect(component.loadData).toHaveBeenCalled();
expect(apiServiceMock.apiGet).toHaveBeenCalled()
expect(component.isLoading).toBe(true);
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