Testing HTTP calls with HttpTestingController in Angular - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is HttpTestingController used for in Angular testing?

HttpTestingController lets you mock and verify HTTP requests in Angular tests without making real network calls.

beginner

How do you inject HttpTestingController in an Angular test?

Use Angular's TestBed.inject(HttpTestingController) inside your test setup to get the controller instance.

beginner

What method do you use to expect a specific HTTP request in your test?

Use httpTestingController.expectOne(urlOrPredicate) to find and assert a single HTTP request matching the URL or condition.

intermediate

How do you simulate a response to an HTTP request in tests?

Call req.flush(data) on the matched request to send back mock data as the HTTP response.

intermediate

Why should you call httpTestingController.verify() at the end of your test?

It checks that no unexpected HTTP requests are left outstanding, ensuring your test covers all HTTP calls.

Which Angular service helps you mock HTTP requests in tests?

A HttpClient

B HttpClientModule

C HttpTestingController

D HttpInterceptor

HttpTestingController is designed for mocking and verifying HTTP requests in Angular tests.

What does expectOne() do in HttpTestingController?

A Mocks multiple HTTP requests

B Finds exactly one matching HTTP request

C Cancels all HTTP requests

D Sends a real HTTP request

expectOne() finds and returns a single HTTP request matching the given criteria.

How do you simulate a server response in an Angular HTTP test?

A Use <code>subscribe()</code> on HttpTestingController

B Call <code>send()</code> on HttpClient

C Call <code>verify()</code> on HttpClient

D Call <code>flush()</code> on the matched request

flush() sends mock data as the HTTP response in tests.

Why is httpTestingController.verify() important?

A It ensures no unexpected HTTP requests remain

B It sends all pending HTTP requests

C It resets the HTTP client

D It logs HTTP requests to console

verify() confirms all expected HTTP requests were handled and none are left open.

Where do you usually inject HttpTestingController in Angular tests?

A Inside the test setup using <code>TestBed.inject()</code>

B In the component constructor

C In the service constructor

D In the main app module

Inject HttpTestingController in the test setup to control HTTP requests during testing.

Explain how to test an Angular service's HTTP GET call using HttpTestingController.

Think about the steps to mock and verify the HTTP call in a test.

Describe why mocking HTTP calls is better than making real HTTP requests in Angular tests.

Consider what makes tests stable and fast.