Typescript: Tests: no way ensuring that super has been called.

[Izhaki]

When writing tests (using Jasmine in my case), how can one ensure that the super of a class is called?

For instance, in the following code:

class Snake extends Animal {
    constructor(name: string) { super(name); }
    move(meters = 5) {
        alert("Slithering...");
        super.move(meters);
    }
}

How can one write a test ensuring super.move() is called when Snake.move() is called?

[bmayen]

Should be able to spy on it and then check if it was called with toHaveBeenCalled

[DanielRosenwasser]

For the record, StackOverflow/StackExchange/our Gitter room/our IRC room is probably a better venue for these sorts of questions.

[Izhaki]

@bmayen how?

I can't see super anywhere on the prototype.

@DanielRosenwasser, might be phrased as a question, but I'm really arguing this cannot be done and thus an issue.

[mhegazy]

there is no entity called super super is just an alias to the class you are extending. in this case, Animal. so as @bmayen mentioned, Animal.move is what you want to check to have been called.

[Izhaki]

@mhegazy Still not sure I understand. Animal is a class, not an instance.

Just to make it more concrete, given this code:

class Painter extends Transformer {

    //.... 

    translate( aTranslation: Point ) {
        this.context.translate( aTranslation.x , aTranslation.y );
        super.translate( aTranslation );
    }

}

The test:

describe( 'translate()', function() {

    beforeAll( function () {
        spyOn( iPainter.context, 'translate' );
        iPainter.translate( new Point( 10, 20 ) );
    });

    it( 'Should translate the context', function() {
        expect( iPainter.context.translate ).toHaveBeenCalledWith( 10, 20 );
    });

    it( 'Should call translate on its super', function() {
        // What's here???
    });        

});

What would be the line to replace What's here???

[mhegazy]

var originalTransformenrTranslate = Transformer. prototype.translate;
Transformer. prototype.translate = function (...args) {
    console.log("Transformer.translate is called!");
    originalTransformenrTranslate.apply(this, args);
}

var originalPainterTranslate = Painter. prototype.translate;
Painter. prototype.translate = function (...args) {
    console.log("Painter.translate is called!");
    originalPainterTranslate.apply(this, args);
}

[Izhaki]

Or alternatively:

beforeAll( function () {
    spyOn( Transformer.prototype, 'translate' );

    iTranslation = new Point( 10, 20 );
    iPainter.translate( iTranslation );
});

it( 'Should call translate on its super', function() {
    expect( Transformer.prototype.translate ).toHaveBeenCalledWith( iTranslation );
});

Got it, thanks!