Guide on creating a Jasmine test for a printer utility

Currently, I am working on writing a Jasmine test for the print function shown below:

  printContent( contentName: string ) {
    this._console.Information( `${this.codeName}.printContent: ${contentName}`)
    let printContents = document.getElementById( contentName ).innerHTML;
    const windowPrint = window.open('', '', 'left=0,top=0,width=925,height=1400,toolbar=0,scrollbars=0,status=0');
    windowPrint.document.write(printContents);
    windowPrint.document.close();
    windowPrint.focus();
    windowPrint.print();
    windowPrint.close();
  }

I am open to modifying the function to make it more easily testable. This is the current test I have written:

  it( 'printContent should open a window ...', fakeAsync( () => {
    spyOn( window, 'open' );
    sut.printContent( 'printContent' );
    expect( window.open ).toHaveBeenCalled();
  }) );

Improving code coverage is my main goal at the moment.

javascriptangulartypescriptjasmine

Answer №1

It is crucial to ensure that the window.open() function returns a fully functional object, as the printContent method being tested relies on properties and functions of this object named windowPrint. Typically, such an object can be created using the createSpyObj method.

var doc = jasmine.createSpyObj('document', ['write', 'close']);
var windowPrint = jasmine.createSpyObj('windowPrint', ['focus', 'print', 'close']);
windowPrint.document = doc; 
spyOn(window, 'open').and.returnValue(windowPrint);

The modified unit test would then appear as follows:

it( 'printContent should open a window ...', () => {

  // given
  var doc = jasmine.createSpyObj('document', ['write', 'close']);
  var windowPrint = jasmine.createSpyObj('windowPrint', ['focus', 'print', 'close']);
  windowPrint.document = doc;
  spyOn(window, 'open').and.returnValue(windowPrint);

  // when
  sut.printContent('printContent');

  // then
  expect(window.open).toHaveBeenCalledWith('', '', 'left=0,top=0,width=925,height=1400,toolbar=0,scrollbars=0,status=0');
  expect(doc.write).toHaveBeenCalled(); 
  expect(doc.close).toHaveBeenCalled(); 
  expect(windowPrint.focus).toHaveBeenCalled(); 
  expect(windowPrint.print).toHaveBeenCalled(); 
  expect(windowPrint.close).toHaveBeenCalled(); 
});

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