angular-unit-test-helper
v17.1.0
Published
Helper functions to help write unit tests in Angular using mocks and spies
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Angular Unit Test Helper
Helper functions to help write unit tests in Angular using mocks and spies
Breaking Changes
createComponentMock
has been removed, in favor ofng-mocks
. See below for more info.
Goal
Minimal feature set to bridge obvious gaps in jasmine's support of modern JavaScript features. Ideally, I'd like to be using an auto-mocking library, but they don't play well with Angular's TestBed
and RxJS\BehaviorSubject
.
Here's a great article about auto-mocking libraries: https://hackernoon.com/with-typescript-3-and-substitute-js-you-are-already-missing-out-when-mocking-or-faking-a3b3240c4607.
Install
Add the package to your Angular project with npm:
npm i -D angular-unit-test-helper
Example Projects
Check out my sample projects that leverage angular-unit-test-helper
:
- https://github.com/duluca/local-weather-app
- https://github.com/duluca/lemon-mart
Use the ng-tester
package to generate robust and efficient unit tests using angular-unit-test-helper
.
Usage
npm i -D ng-tester
npx ng g ng-tester:unit
For more information see https://github.com/bjsawyer/ng-tester/.
Features
autoSpyObj(classUnderTest: Function, spyProperties: string[] = [], observableStrategy = ObservablePropertyStrategy.Observable)
An extension of jasmine.createSpyObj
with automatic discovery of functions and property getters given a Class, without requiring an instance of an object.
If you'd want to spy on a property without a getter, then you can simply pass in the property name like autoSpyObj(WeatherService, ['currentWeather$'])
.
Return value of autoSpyObj
will be a true mock of the Class with spy-able methods and properties, making it easy to control and modify the return values of external dependencies during testing.
If property name ends with $
indicating that the property is an Observable, then you can specify an optional ObservablePropertyStrategy
to prefer {}
, new Observable()
or new BehaviorSubject(null)
default values for your mocked properties.
Usage
const weatherServiceSpy = autoSpyObj(WeatherService)
Alternate Usage
const weatherServiceSpy = autoSpyObj(
WeatherService,
['currentWeather$'],
ObservablePropertyStrategy.BehaviorSubject
)
autoSpyObj
replaces the more verbose and difficult to maintain code, shown below:
jasmine.createSpyObj(WeatherService.name, [
'getCurrentWeather',
'getCurrentWeatherByCoords',
'updateCurrentWeather',
])
addPropertyAsBehaviorSubject(weatherServiceSpy, 'currentWeather$')
addProperty(object: object, propertyName: string, valueToReturn: object)
When creating a mock object, add a property to that object with a property getter, so you can use a jasmine.spyOnProperty.
Usage
weatherServiceMock = jasmine.createSpyObj('WeatherService', ['getCurrentWeather'])
addPropertyAsBehaviorSubject(weatherServiceMock, 'currentWeather', null)
...
spyOnProperty(weatherServiceMock, 'currentWeather$').and.returnValue({ temp = 72})
addPropertyAsBehaviorSubject(object: object, propertyName: string)
Convenience method to configure a property as a BehaviorSubject, so you can update its value before each test by calling .next on it.
Usage
weatherServiceMock = jasmine.createSpyObj('WeatherService', ['getCurrentWeather'])
addPropertyAsBehaviorSubject(weatherServiceMock, 'currentWeather$')
...
weatherServiceMock.currentWeather$.next(fakeWeather)
deprecated createComponentMock(className: string, selectorName?: string, template = '')
Deprecated Use ng-mocks
instead. https://ng-mocks.sudo.eu/api/MockComponent.
- Install using
install i -D ng-mocks
- Refactor
createComponentMock
function calls to look like the sample below:
TestBed.configureTestingModule({
declarations: [
// for a single component
MockComponent(Component),
// for a set of components
...MockComponents(Component1, Component2),
],
})
Creates a mock class decorated with @Component, if not specified selector is inferred to be MyClassComponent -> app. Provides an option to override empty template.
Usage
TestBed.configureTestingModule({
declarations: [ ..., createComponentMock('CurrentWeatherComponent')]
...
})
Note: Inferred selector in the above example is 'app-current-weather'.
Replaces boilerplate
@Component({
selector: 'app-current-weather',
template: '',
})
class MockCurrentWeatherComponent {}
getNativeElementByTestId<TComponent>(fixture: ComponentFixture<TComponent>, testId: string = '')
Helper function to retrieve the native element associated with a specific `data-testid`` within a component fixture.
Usage
<span class="left-pad" data-testid="title">LemonMart</span>
it('should render title', () => {
const fixture = TestBed.createComponent(AppComponent)
fixture.detectChanges()
const titleElement = getNativeElementByTestId(fixture, 'title')
expect(titleElement.textContent).toContain('LemonMart')
})
injectClass<TDependency>(dependency: Type<TDependency> | AbstractType<TDependency>): TDependency
Helper function to inject a dependency, like a service, into the TestBed with a typed return variable.
Usage
beforeEach(() => {
weatherService = injectClass(WeatherService)
})
Replaces
beforeEach(() => {
weatherService = TestBed.inject(WeatherService)
})
injectSpy<TDependency>(dependency: Type<TDependency> | AbstractType<TDependency>): jasmine.SpyObj<TDependency>
Similar to injectClass
, but more descriptive to read for developers if returning a mocked SpyObj.
Usage
beforeEach(() => {
weatherServiceMock = injectSpy(WeatherService)
})
Replaces
beforeEach(() => {
weatherServiceMock = TestBed.inject(WeatherService) as any
})
getAllFunctions(prototype: any, props?: (string | number | symbol)[])
Helper function that return all functions in a given Class using reflection, so you don't have to provide an instance of the object.
getAllProperties(prototype: any, props?: (string | number | symbol)[])
Helper function that return all property getters in a given Class using reflection, so you don't have to provide an instance of the object.
Contributing
- Send PR, will accept
- To setup the project, run
npm install
- Test against the example project listed below using
npm pack
to create a.tgz
file and install the.tgz
file usingnpm install -D ../path/to/your.tgz
- Using
npm link
doesn't work as expected duedevDependencies
being symlinked to the parent Angular project, causing issues with the framework.
- Using
- To publish the project, run
npm version major|minor|patch
Read more about that setup by Isaac Schlueter here