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I am working with angular-tree-component to show a category tree in a stateless component in angular. Currently, I have up and running the component and is time to make some unit tests. I am experiencing a problem because I want to test a function that executes the method update() of treeModel, which is the property of the tree component that exposes the API of angular-tree-component. (See documentation here).

My function, called updateTree() just run update() on treeModel as below:

export class CategoryTreeComponent implements AfterViewInit {

  @ViewChild('tree') treeComponent: TreeComponent;
  treeModel: TreeModel;

  constructor() {
  }

  ngAfterViewInit() {
    debugger;
    this.treeModel = this.treeComponent.treeModel;
  }

  updateTreeFn() {
    this.treeModel.update();
  }

}

So, I had written my unit test as shown below.

it('should call update method of treeModel', () => {    
  component.ngAfterViewInit();
  fixture.detectChanges();
  const spy = spyOn(component.treeModel, 'update');
  component.updateTree();
  expect(spy).toHaveBeenCalled();  
});

The problem is that treeModel is always undefined. I notice that treeModel is a class property of type TreeModel on TreeComponent Class and update is a method of TreeModel object. Probably, this is why I am getting that error.

Any ideas on how I can test that update method is called and recognize treeModel object to spy it.

xzegga
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1 Answers1

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recently I had similar problem, wrapping my test to be executed in the fakeAsync zone did the trick :

it('should call update method of treeModel', fakeAsync(() => {    
  component.ngAfterViewInit();
  tick(100);
  fixture.detectChanges();
  const spy = spyOn(component.treeModel, 'update');
  component.updateTree();
  tick(100);
  expect(spy).toHaveBeenCalled();  
}));

But I'm not sure about spying treeModel's methods ...

Michał Piech
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