In Angular, when using a hot observable, what happens to the data emissions when there are no subscribers?
- Data emissions are buffered and sent to the next subscriber when they subscribe.
- Data emissions are cached and sent to the first subscriber who subscribes.
- Data emissions are lost if there are no subscribers.
- Data emissions are sent to a separate storage location for later retrieval.
When using a hot observable in Angular, data emissions are lost if there are no subscribers. They are not cached or buffered for future subscribers.
You are writing a test for an Angular component that renders a list of items. You want to test that when a new item is added, it is correctly displayed in the component. Which testing technique or utility would be best suited for this?
- End-to-End Testing with Protractor
- Integration Testing with Karma and Jasmine
- No testing needed - it's an Angular feature
- Unit Testing with TestBed
For testing component behavior in isolation, Unit Testing with TestBed is the most suitable approach. It allows you to create an isolated testing environment for the component.
What is the role of fixture in Angular component tests?
- Hold data
- Manage test configuration
- Render the component
- Simulate user interactions
The role of the fixture in Angular component tests is to render the component for testing and provide a handle for simulating user interactions.
How can you test that a directive correctly responds to changes in input values?
- Directly manipulate the directive's DOM elements and observe changes
- Manually update the directive's input values and check the DOM
- Use the TestBed's detectChanges method to trigger change detection
- Use the ng test CLI command to automate the testing process
To test that a directive correctly responds to input value changes, you should use the TestBed's detectChanges method to trigger change detection.
To perform side-effect-free computations synchronously, Angular provides a testing utility known as _____.
- HttpClientTestingModule
- JasmineSpy
- MockAsyncService
- TestBed
To perform side-effect-free computations synchronously in Angular, you can use the TestBed utility for creating and configuring testing modules.
In Angular, the replaceUrl property of the _____ object can be used to navigate while replacing the current URL in the browser's history.
- ActivatedRouteSnapshot
- NavigationExtras
- Router
- RouterStateSnapshot
In Angular, the replaceUrl property of the RouterStateSnapshot object can be used to navigate while replacing the current URL in the browser's history. It allows for URL manipulation.
When testing a directive that modifies the DOM, what should you consider to ensure that the tests are not flaky?
- Avoid testing such directives as they are inherently flaky
- Check for DOM changes in a loop until they are detected consistently
- Use a stubbed version of the directive to isolate DOM changes
- Use asynchronous timers to delay test execution until the DOM changes
To prevent flaky tests when testing a directive that modifies the DOM, use a stubbed version of the directive to isolate DOM changes and ensure reliable testing.
What does the async pipe do in an Angular template?
- Handles routing
- Renders HTML
- Subscribes to an Observable
- Transforms data
The async pipe in an Angular template subscribes to an Observable and automatically updates the view with the most recent data emitted by the Observable. It simplifies working with asynchronous data in templates.
Which lifecycle hook is best suited to react to changes in a component's input properties?
- ngAfterViewInit
- ngDoCheck
- ngOnChanges
- ngOnInit
The ngOnChanges lifecycle hook is best suited to react to changes in a component's input properties. It provides information about the changes to input properties.
When using Jasmine and Karma for testing, how can you ensure that a specific test or suite of tests is executed while others are ignored?
- Apply a custom test filter
- Enable verbose logging
- Set a test timeout
- Use the "xit" or "fdescribe" keywords
In Jasmine and Karma testing, you can ensure that a specific test or suite of tests is executed while others are ignored by using the "xit" (exclude it) or "fdescribe" (focus describe) keywords.