ngx-test-helpers

Various helper methods for testing Angular applications with Jasmine.

Install ngx-test-helpers as dev dependency.

npm install ngx-test-helpers --save-dev

setupComponentTest

function setupComponentTest(moduleDef: TestModuleMetadata): void

Angular resets its testing module for each single test. This ensures that all tests run in complete isolation from each other. While this is the ideal situation for running unit tests, it comes with a heavy price regarding performance. Many tests may be perfomed without resetting the testing module. Currently, there is no official way to prevent the reset, however there is a workaround described in this GitHub issue. Basically, after configuring the testing module, the TestBed.resetTestingModule method is replaced with a dummy implementation. This happens in a beforeAll block which is run once before the specs in a describe block are executed. In an afterAll block the TestBed.resetTestingModule method is restored after the tests of the describe block have been executed.

setupComponentTest wraps this workaround and combines it with configureComponentTestEnvironment.

API

Param	Type	Description
moduleDef	TestModuleMetadata	Angular module definition as passed to TestBed.configureTestingModule.

Example

describe('AppComponent', () => {
    let fixture: ComponentFixture<AppComponent>;

    setupComponentTest({
        declarations: [
            AppComponent
        ]
    });

    beforeEach(() => {
        fixture = createComponent(AppComponent);
    });

    it('should create', () => {
        expect(fixture.componentInstance).toBeTruthy();
    });
});

configureComponentTestEnvironment

function configureComponentTestEnvironment(moduleDef: TestModuleMetadata): void

Configures the testing module with given module definition and NO_ERRORS_SCHEMA and compiles the components. Use this method in a beforeEach block if you don't want to use the performance workaround implemented by setupComponentTest.

NO_ERRORS_SCHEMA allows any property on any element so that components can be compiled even if directives, which are irrelevant to the use case being tested, aren't imported.

API

Param	Type	Description
moduleDef	TestModuleMetadata	Angular module definition as passed to TestBed.configureTestingModule.

Example

describe('AppComponent', () => {
    let fixture: ComponentFixture<AppComponent>;

    beforeEach(() => {
        configureComponentTestEnvironment({
            declarations: [
                AppComponent
            ]
        });
        fixture = createComponent(AppComponent);
    });

    it('should create', () => {
        expect(fixture.componentInstance).toBeTruthy();
    });
});

mergeModuleDefs

function mergeModuleDefs(...moduleDefs: TestModuleMetadata[]): TestModuleMetadata

Merges two or more Angular module definitions. Useful if you want to combine an externally defined default definition with a local one.

API

Param	Type	Description
...moduleDef	TestModuleMetadata	Two or more Angular module definitions.

Example

describe('AppComponent', () => {
    setupComponentTest(mergeModuleDefs(
        getModuleDefForStore(reducerConfig), // returns a module definition with everything needed to setup the ngrx store
        {
            declarations: [
                AppComponent
            ]
        }
    ));
});

createComponent

function createComponent<T>(component: Type<T>): ComponentFixture<T>

Creates a ComponentFixture for the given component. Just a wrapper for TestBed.createComponent so that you don't need to mix TestBed methods with methods from this helper.

Param	Type	Description
component	Type<T>	The component to be created.

Example

describe('AppComponent', () => {
    let fixture: ComponentFixture<AppComponent>;

    beforeEach(() => {
        configureComponentTestEnvironment({
            declarations: [
                AppComponent
            ]
        });
        fixture = createComponent(AppComponent);
    });

    it('should create', () => {
        expect(fixture.componentInstance).toBeTruthy();
    });
});

forceChangeDetection

function forceChangeDetection<T>(fixture: ComponentFixture<T>): void

When testing components that are configured with an OnPush change detection strategy, a call to fixture.detectChanges() does not trigger Angular's change detection to run. Change detection for those components only runs when the host component passes new values. One way to solve this issue in unit tests is to use a test host component. However, this is cumbersome and pollutes tests with a lot of boilerplate code. A workaround for this issue is a hack described in a comment in this GitHub issue. This method wraps the workaround in a convenient method.

As this method directly accesses internal, non-public properties of Angular, it should be noted that this method may fail in a future Angular version.

API

Param	Type	Description
fixture	ComponentFixture<T>	The component fixture for the expectation.

Example

it('should create', () => {
    fixture.componentIntance.buttonIsDisabled = true;

    forceChangeDetection(fixture);

    expectElementFromFixture(fixture, 'button').toBeDisabled();
});

expectComponent

function expectComponent<T>(fixture: ComponentFixture<T>): jasmine.Matchers<T>

Wraps the fixture's component instance in an expect call.

API

Param	Type	Description
fixture	ComponentFixture<T>	The component fixture for the expectation.

Example

it('should create', () => {
    expectComponent(fixture).toBeTruthy();
});

expectElementFromFixture

function expectElementFromFixture<T>(fixture: ComponentFixture<T>, domQuery?: string): jasmine.Matchers<{}>

Write expectations for the component's root element or for one of its child elements. Useful in combination with Jasmine Dom Matchers.

API

Param	Type	Description
fixture	ComponentFixture<T>	The component fixture for the expectation.
domQuery	string	(optional) A DOM query as required by Element.querySelector. If omitted, the component's root element itself is used.

Example

This example uses Jasmine Dom Matchers.

it('should be rendered as block-level element', () => {
    expectElementFromFixture(fixture).toHaveCss({ display: 'block' });
});

it('contain a title', () => {
    expectElementFromFixture(fixture, 'h1').toContainText('Hello World');
});

expectElementsFromFixture

function function expectElementsFromFixture<T>(fixture: ComponentFixture<T>, domQuery: string): jasmine.ArrayLikeMatchers<{}>

Write expectations for an array of HTML elements.

API

Param	Type	Description
fixture	ComponentFixture<T>	The component fixture for the expectation.
domQuery	string	A DOM query as required by Element.querySelectorAll.

Example

This example uses Jasmine-Matchers.

it('should contain a list of 10 items', () => {
    expectElementsFromFixture(fixture, 'ul > li').toBeArrayOfSize(10);
});

expectFormElementFromFixture

function expectFormElementFromFixture<T>(fixture: ComponentFixture<T>, formControlName: string): jasmine.Matchers<{}>

Write expectations for a form control.

API

Param	Type	Description
fixture	ComponentFixture<T>	The component fixture for the expectation.
formControlName	string	A form control name as defined by Angular's formControlName directive.

Example

This example uses Jasmine Dom Matchers.

it('has a disabled comment field', () => {
    expectFormElementFromFixture(fixture, 'comment').toBeDisabled();
});

expectViewChildFromFixture

function expectViewChildFromFixture<T>(fixture: ComponentFixture<T>, viewChildProperty: string): jasmine.Matchers<{}>

Write expectations for a component's view child.

API

Param	Type	Description
fixture	ComponentFixture<T>	The component fixture for the expectation.
viewChildProperty	string	The name of the component's property which is annotated as ViewChild.

Example

This example uses Jasmine Dom Matchers.

// component-with-view-child.ts
@Component({
    selector: 'app-root',
    template: `
        <main>
            <app-child-component #child></child-component>
        </main>
    `
})
export class AppComponent {

    @ViewChild('child')
    child: ChildComponent;

}

it('has a child that is rendered as block-level element', () => {
    expectViewChildFromFixture(fixture, 'child').toHaveCss({ display: 'block' });
});

componentFromFixture

function componentFromFixture<T>(fixture: ComponentFixture<T>): T

Returns the fixture's component instance.

API

Param	Type	Description
fixture	ComponentFixture<T>	The fixture for which to return the component instance.

Example

This example uses Jasmine Dom Matchers.

it('exposes a reset method that resets the form', () => {
    componentFromFixture(fixture).reset();
    
    formElementFromFixture(fixture, 'firstName').toHaveValue('');
});

viewChildFromFixture

function viewChildFromFixture<T>(fixture: ComponentFixture<T>, viewChildProperty: string): Element

Returns the view child's DOM element.

API

Param	Type	Description
fixture	ComponentFixture<T>	The component fixture for the expectation.
viewChildProperty	string	The name of the component's property which is annotated as ViewChild.

Example

it('has a disabled comment field', () => {
    const form = viewChildFromFixture(fixture, 'commentForm');

    expect(form.querySelector('textarea#comment').disabled).toBeTrue();
});

formElementFromFixture

function formElementFromFixture<T>(fixture: ComponentFixture<T>, formControlName: string): Element

Returns the DOM for a form control.

API

Param	Type	Description
fixture	ComponentFixture<T>	The component fixture for the expectation.
formControlName	string	A form control name as defined by Angular's formControlName directive.

Example

it('has a disabled comment field', () => {
    const commentField = formElementFromFixture(fixture, 'comment');

    expect(commentField.disabled).toBeTrue();
});

elementFromFixture

function elementFromFixture<T>(fixture: ComponentFixture<T>, domQuery?: string): Element

Returns a DOM element from within the component matching the query.

API

Param	Type	Description
fixture	ComponentFixture<T>	The component fixture for the expectation.
domQuery	string	(optional) A DOM query as required by Element.querySelector. If omitted, the component's root element itself is used.

Example

it('has a disabled comment field', () => {
    const commentField = elementFromFixture(fixture, 'textarea#comment');
    expect(commentField.disabled).toBeTrue();
});

elementsFromFixture

function elementsFromFixture<T>(fixture: ComponentFixture<T>, domQuery: string): Element[]

Returns an array of DOM elements from within the component matching the query.

API

Param	Type	Description
fixture	ComponentFixture<T>	The component fixture for the expectation.
domQuery	string	A DOM query as required by Element.querySelectorAll.

it('checkboxes that are all checked', () => {
    elementsFromFixture(fixture, 'input[type="checkbox"]').forEach(checkbox => {
        expect(checkbox.checked).toBeTrue();
    });
});

childComponentsFromFixture

function childComponentsFromFixture<T>(fixture: ComponentFixture<{}>, domQuery: string): T[]

It returns child components matching the DOM query casted as the given type.

API

Param	Type	Description
fixture	ComponentFixture<T>	The component fixture for the expectation.
domQuery	string	A DOM query as required by Element.querySelectorAll.

Example

it('has a child components which all expose an active property', () => {
    childComponentsFromFixture<ChildComponent>(fixture, 'app-child').forEach(child => {
        expect(child.active).toBeBoolean();
    });
});

ReducerConfig

In order to use ngrx with AOT the reducers have to be provided using an InjectionToken. See this GitHub issue for more details. That is why some methods require a reducerConfig consisting of a ActionReducerMap and an injection token.

export interface ReducerConfig<T> {
    injectionToken: InjectionToken<ActionReducerMap<T>>;
    reducers: ActionReducerMap<T>;
}

Example

export const reducers: ActionReducerMap<AppState> = {
    counter: counterReducer
};

export const reducersInjectionToken = new InjectionToken<ActionReducerMap<AppState>>('Registered Reducers');
Object.assign(reducersInjectionToken, reducers);

export const reducerConfig: ReducerConfig<AppState> = {
    reducers,
    injectionToken: reducersInjectionToken
};

configureEffectsTestEnvironment

function configureEffectsTestEnvironment<T>( EffectsClass: {}, actionsFn: () => Observable<Action>, moduleDef: TestModuleMetadata, reducerConfig: ReducerConfig<T>, appState?: T): void

Configures the testing module for testing the given Effects class according to the ngrx testing guide.

API

Param	Type	Description
EffectsClass	Type	The Effects class to be tested.
actionsFn	() => Observable<Action>	A function that is used by ngrx' provideMockActions method.
moduleDef	TestModuleMetadata	Angular module definition as passed to TestBed.configureTestingModule.
reducerConfig	ReducerConfig<T>	A configuration consisting of the ActionReducerMap and an InjectionToken for the reducer map. See comment above.
appState	T	(optional) An initial app state with which the store is initialised.

Example

describe('CounterEffects', () => {
    let actions: Observable<Action>;
    let counterEffects: CounterEffects;

    beforeEach(() => {
        configureEffectsTestEnvironment(
            CounterEffects,
            () => actions,
            {
                imports: [
                    CounterModule
                ]
            },
            reducerConfig
        );
        counterEffects = TestBed.get(CounterEffects);
    });

    describe('count', () => {
        it('dispatches a new action when something has been counted', () => {
            actions = hot('--a-', { a: new CountAction() });

            counterEffects.count
                .subscribe((dispatchedAction: CountedAction) => {
                    expect(dispatchedAction.type).toBe('Counted')
                });
        });
    });

});

getModuleDefForStore

function getModuleDefForStore<T>(reducerConfig: ReducerConfig<T>, appState?: T): TestModuleMetadata

Returns a module configuration setting up the ngrx store with the given reducers and an initial application state.

API

Param	Type	Description
reducerConfig	ReducerConfig<T>	A configuration consisting of the ActionReducerMap and an InjectionToken for the reducer map. See comment above.
appState	T	(optional) An initial app state with which the store is initialised.

Example

describe('AppComponent', () => {
    let fixture: ComponentFixture<AppComponent>;
    let store: Store<AppState>;

    beforeEach(() => {
        configureComponentTestEnvironment(
            mergeModuleDefs(
                getModuleDefForStore(
                    reducerConfig,
                    {
                        counter: {
                            currentValue: 5
                        }
                    }
                ),
                {
                    imports: [
                        AppModule
                    ]
                }
            )
        );
        store = TestBed.get(Store);
        fixture = createComponent(AppComponent);
    });
});

getAppState

function getAppState<T>(stateFn: (T) => void): void

Calls the given function with the current application state.

API

Param	Type	Description
stateFn	(T) => void	The method to which the app state is passed.

Example

describe('AppComponent', () => {
    let fixture: ComponentFixture<AppComponent>;
    let appState: AppState;

    beforeEach(() => {
        configureComponentTestEnvironment(
            mergeModuleDefs(
                getModuleDefForStore(reducerConfig),
                {
                    imports: [
                        AppModule
                    ]
                }
            )
        );
        getAppState(state => appState = state);
        fixture = createComponent(AppComponent);
    });
});

expectActionToBeDispatched

function expectActionToBeDispatched(fixture: ComponentFixture<{}>, actionType: string, triggerFn?: () => void, payload?: any): void

Tests if the given action has been dispatched. Optionally, a trigger function may be passed which is used to trigger the action.

API

Param	Type	Description
fixture	ComponentFixture<T>	The component fixture for the expectation.
actionType	string	The type of the action to check against.
triggerFn	() => void	A function that leads to the action to be dispatched.
payload	any	Any value to match the action's payload against via isEqual.

Example

it('dispatches a count action when the onClickCount handler is called', () => {
    expectActionToBeDispatched(
        fixture,
        ActionType.Count,#
        () => {
            fixture.componentInstance.onClickCount();
        },
        { value: 1 }
    );
});

expectActionNotToBeDispatched

function expectActionNotToBeDispatched(fixture: ComponentFixture<{}>, actionType: string, triggerFn?: () => void): void

Tests if the given action has not been dispatched. This method is useful if actions are only dispatched under certain conditions.

API

Param	Type	Description
fixture	ComponentFixture<T>	The component fixture for the expectation.
actionType	string	The type of the action to check against.
triggerFn	() => void	A function that normally leads to the action to be dispatched.

Example

it('does not dispatch a count action when counting is disabled', () => {
    fixture.componentInstance.countingDisabled = true;

    expectActionNotToBeDispatched(fixture, ActionType.Count, () => {
        fixture.componentInstance.onClickCount();
    });
});

expectElement

function expectElement(rootElement: Element, domQuery: string): jasmine.Matchers<{}>

Write expectations for a DOM element.

API

Param	Type	Description
rootElement	Element	The root element for the expectation.
domQuery	string	A DOM query as required by Element.querySelector.

Example

it('has a disabled comment field', () => {
    const componentElement = elementFromFixture(fixture);

    expectElement(componentElement, 'textarea#comment').disabled).toBeTrue();
});

expectElements

function expectElements(rootElement: Element, domQuery: string): jasmine.ArrayLikeMatchers<{}>(')

Write expectations for an array of DOM elements.

API

Param	Type	Description
rootElement	Element	The root element for the expectation.
domQuery	string	A DOM query as required by Element.querySelectorAll.

Example

This example uses Jasmine-Matchers.

it('should contain a list of 10 items', () => {
    const componentElement = elementFromFixture(fixture);
    expectElements(componentElement, 'ul > li').toBeArrayOfSize(10);
});

elementByQuery

function elementByQuery(rootElement: Element, domQuery: string): Element

Returns a child element matching the given DOM query.

API

Param	Type	Description
rootElement	Element	The root element from which to query for a child element.
domQuery	string	A DOM query as required by Element.querySelector.

Example

it('has a disabled comment field', () => {
    const componentElement = elementFromFixture(fixture);

    expect(elementByQuery(componentElement, 'textarea#comment').disabled).toBeTrue();
});

elementsByQuery

function elementsByQuery(rootElement: Element, domQuery: string): Element[]

Returns an array of child elements matching the given DOM query.

API

Param	Type	Description
rootElement	Element	The root element from which to query for child elements.
domQuery	string	A DOM query as required by Element.querySelectorAll.

Example

This example uses Jasmine-Matchers.

it('should contain a list of 10 items', () => {
    const componentElement = elementFromFixture(fixture);
    expect(elementsByQuery(componentElement, 'ul > li')).toBeArrayOfSize(10);
});

childComponentsByQuery

function childComponentsByQuery<T>(rootElement: Element, domQuery: string): T[]

Returns an array of child elements matching the given DOM query casted as the given type.

API

Param	Type	Description
rootElement	Element	The root element from which to query for child elements.
domQuery	string	A DOM query as required by Element.querySelectorAll.

Example

it('has a child components which all expose an active property', () => {
    const componentElement = elementFromFixture(fixture);
    childComponentsByQuery<ChildComponent>(componentElement, 'app-child').forEach(child => {
        expect(child.active).toBeBoolean();
    });
});