Testing Generic Angular Components (not Generic Class)

Question

Is it possible to test an Angular Generic Component?

As an example, if I have

@Component({
    ...
})
export class MyComponent<T> implements OnInit {
   public constructor(
      private context: T
   );
}

Where T can be any number of classes.

Then eventually I want to write a Jasmine test, but I am not able to determine the proper syntax for when creating the test fixture:

fixture = TestBed.createComponent(MyComponent<MyTestObject>);

It is here that TSLint complains:

Value of type 'typeof MyComponent' is not callable. Did you mean to include new?

It clearly thinks that I need a constructor (?), but is unclear how or where to implement that.

Is what I am attempting even possible? I can find examples of generic components. I can't find examples on setting up a test fixture / component

user9578963 · Accepted Answer · 2021-02-13 14:00:19Z

5

The TestBed.createComponent function in itself is generic and returns a componentFixture, so that is where you should apply the generic. For your use-case you should do:

fixture = TestBed.createComponent<MyComponent<MyTestObject>>(MyComponent);

Remember to have declared your fixture as

let fixture: ComponentFixture<MyComponent<MyTestObject>>;

answered Feb 13, 2021 at 14:00

user9578963

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Comments

John · Accepted Answer · 2019-05-28 22:03:14Z

3

I imagine that TestBed.createComponent() expects a javascript class as an argument. MyComponent<MyTestObject> is not valid javascript.

Perhaps you intended to put TestBed.createComponent(MyComponent as typeof MyComponent<MyTestObject>) (or maybe the proper syntax is MyComponent as (typeof MyComponent)<MyTestObject> -- I'm not sure).

Alternatively, if TestBed#createComponent() is generic, you'd probably want to do TestBed.createComponent<MyComponent<MyTestObject>>(MyComponent).

answered May 28, 2019 at 22:03

John

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1 Comment

Deunz Over a year ago

This doesn't work =) still interested in this matter

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