Simpler, cleaner Angular unit tests
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README.md

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ngx-speculoos

ngx-speculoos helps you write simpler, cleaner unit tests for your Angular components, based on the page object pattern. It also provides utilities to make writing Angular unit tests easier.

The library simply wraps the standard Angular ComponentFixture, and you should thus be able to understand and start using ngx-speculoos in just a few minutes if you already know how to write Angular unit tests.

Why should you care?

If you've ever written tests like the following:

it('should display French cities when selecting the country France', () => {
  const countrySelect = fixture.nativeElement.querySelector('#country'); // countrySelect is of type any
  countrySelect.selectedIndex = 12; // what is at index 12?
  countrySelect.dispatchEvent(new Event('change')); // why do I need to do that?
  fixture.detectChanges();
  
  const city = fixture.nativeElement.querySelector('#city'); // city is of type any
  expect(city).toBeTruthy();
  expect(city.options.length).toBe(3);
  expect(city.options[0].value).toBe('');
  expect(city.options[0].label).toBe('');
  expect(city.options[1].value).toBe('PARIS');
  expect(city.options[1].label).toBe('Paris');
  expect(city.options[2].value).toBe('LYON');
  expect(city.options[2].label).toBe('Lyon');
});

it('should hide cities when selecting the empty country option', () => {
  const countrySelect = fixture.nativeElement.querySelector('#country'); // I did that previously. What about DRY?
  countrySelect.selectedIndex = 0;
  countrySelect.dispatchEvent(new Event('change')); // why do I need to do that?
  fixture.detectChanges(); // why do I need to do that?
  
  expect(fixture.nativeElement.querySelector('#city')).toBeFalsy(); // I did that previously. What about DRY?
});

ngx-speculoos allows writing the above tests in a simpler, cleaner way:

  • by using the page object pattern (which is optional, but recommended), you avoid repetitions.
  • by using wrappers around elements, dispatching events and triggering change detection is automatic.
  • by using wrappers around elements, you get useful additional methods to make tests easier to write and read.
  • by using custom matchers, you get even simpler expectations and more readable error messages
  • in any case you need them, you always have access to the fixture, the native elements, the debug elements, etc.
class MyComponentTester extends ComponentTester<MyComponent> {
  constructor() {
    super(MyComponent);
  }
  
  get country() {
    return this.select('#country'); // returns a TestSelect object, not any. Similar methods exist for inputs, buttons, etc.
  }
  
  get city() {
    return this.select('#city'); // returns a TestSelect object, not any
  }
}

[...]

it('should display French cities when selecting the country France', () => {
  tester.country.selectLabel('France'); // no dispatchEvent, no detectChanges needed
  
  expect(tester.city.optionValues).toEqual(['', 'PARIS', 'LYON']);
  expect(tester.city.optionLabels).toEqual(['', 'Paris', 'Lyon']);
});

it('should hide cities when selecting empty country option', () => {
  tester.country.selectIndex(0); // no repetition of the selector, no dispatchEvent, no detectChanges needed
  
  expect(tester.city).toBeFalsy(); // no repetition of the selector
});

Custom matchers

If you use Jasmine, we also have custom matchers for frequent expectations:

  beforeEach(() => jasmine.addMatchers(speculoosMatchers));

  it('should contain a pre-populated form', () => {
    expect(tester.informationMessage).toContainText('Please check that everything is correct');
    expect(tester.country).toHaveSelectedValue('FR');
    expect(tester.city).toHaveSelectedLabel('Paris');
    expect(tester.name).toHaveValue('Doe');
    expect(tester.newsletter).toBeChecked();
  });

The complete matcher list includes:

  • toHaveClass(className: string)
  • toHaveValue(value: string)
  • toHaveText(textContent: string)
  • toContainText(textContent: string)
  • toBeChecked()
  • toHaveSelectedIndex(index: number)
  • toHaveSelectedValue(value: string)
  • toHaveSelectedLabel(label: string)

Installation

Using npm: npm install --save-dev ngx-speculoos

Using yarn: yarn add --dev ngx-speculoos

Getting started

  • import ComponentTester, and other needed classes from ngx-speculoos
  • Create a MyComponentTester class (in your my-component.spec.ts file, typically) extending ComponentTester<MyComponent>, as shown above.
  • Expose getters (or methods, if you prefer) returning the elements used in your tests, using one of the ComponentTester methods (element, elements, input, select, textarea, button). See the API documentation for details
  • Write your tests, as shown above, benefitting from the additional methods on the TestXxx classes.
  • If needed, you can always get the fixture, componentInstance, debugElement, nativeElement, etc. from the ComponentTester, and the nativeElement from each TestXxx wrapper.
  • If you like our custom matchers, add them in a beforeEach block as shown above, and enjoy.

Issues, questions

Please, provide feedback by filing issues, or by submitting pull requests, to the Github Project.

Complete example

You can look at a minimal complete example in the demo project.