fixture.whenStable返回一个Promise，其结果被异步处理。因此，单元测试甚至在调用任何expect之前就结束了。

fakeAsync必须与tick或flush一起使用，以便以同步方式模拟异步处理。尝试如下重写测试。

it('test',fakeAsync(() => {
    fixture.whenStable().then(() => {
        editComponent = component.editComponent;
        editComponent.ruleForm = new FormGroup({
            title: new FormControl('test field'),cause: new FormControl('test field'),});
        fixture.detectChanges();
        spyOn(ruleEditComponent,'updateRule').withArgs(activeIssueId);
        component.saveRuleDetails(activeIssueId);        
    });
    tick();
    expect(editComponent.createRule).toHaveBeenCalledWith(activeIssueId);
}));

或者，您可以按以下方式使用done函数。

it('test',(done) => {
    fixture.whenStable().then(() => {
        editComponent = component.editComponent;
        editComponent.ruleForm = new FormGroup({
            title: new FormControl('test field'),'updateRule').withArgs(activeIssueId);
        component.saveRuleDetails(activeIssueId);        
        expect(editComponent.createRule).toHaveBeenCalledWith(activeIssueId);
        done();
    });        
}));