What is the best way to spy on a property being called within a function?

I am facing an issue where the 'offsetWidth' value is undefined and I need to spyOn it. The function getCurrentPage retrieves an element based on the id currentpage.

Although spying on getCurrentPage works, I have been unable to declare the offsetWidth successfully.

Functions:

getCurrentPage() {
    return this.$document[0].getElementById('currentPage');
}

calculateStep() {
    this.stepWidth = this.getCurrentPage().offsetWidth / (this.totalSteps - 1);
    return this.stepWidth;
}

Unit test:

let stepWidth = new StepController();
stepWidth.totalSteps = 5;

const dummyCurrentPage = '<div id="currentPage" style="width: 20%;"></div>';

spyOn(stepWidth, 'getCurrentPage').and.returnValue(dummyCurrentPage);

const expectedResult = '200 / 4';

const result = stepWidth.calculateStep();

expect(result).toBe(expectedResult);
});

I am trying to figure out how to spyOn the offsetWidth of this.getCurrentPage().offsetWidth?

Answer №1

Successfully located the solution by converting dummyCurrentPage to an angular.element and setting the offsetWidth to match.

const newElement = angular.element('<div id="currentPage" style="width: 20%;"></div>');

dummyCurrentPage.offsetWidth = 50;

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