TestBed configuration in Angular - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is TestBed in Angular testing?

TestBed is Angular's primary API for writing unit tests. It allows you to configure and create an Angular testing module that mimics an Angular @NgModule, so you can test components, services, and other parts in isolation.

beginner

How do you configure a testing module with TestBed?

You use TestBed.configureTestingModule({ declarations: [...], imports: [...], providers: [...] }) to set up components, modules, and services needed for your test.

intermediate

Why do you call TestBed.compileComponents() after configuring TestBed?

Calling compileComponents() compiles the declared components' templates and CSS asynchronously. This is needed before creating component instances in tests.

beginner

What is the purpose of TestBed.createComponent()?

It creates an instance of a component along with its template and styles inside the testing environment. This lets you interact with the component as if it was running in the app.

intermediate

How can you provide a mock service in TestBed configuration?

In the providers array, use { provide: RealService, useClass: MockService } to replace the real service with a mock version during tests.

Which TestBed method sets up the testing module with components and services?

A configureTestingModule

B createComponent

C compileComponents

D inject

configureTestingModule is used to define declarations, imports, and providers for the test module.

What does TestBed.createComponent() return?

A A compiled module

B A component fixture with access to the component instance and DOM

C A service instance

D A promise

createComponent returns a fixture that lets you access the component instance and its rendered DOM.

Why might you use useClass in TestBed providers?

A To declare a component

B To import a module

C To compile templates

D To replace a real service with a mock service

useClass allows you to provide a different class (like a mock) instead of the real service.

When should you call compileComponents() in TestBed?

A After configureTestingModule and before creating components

B Before configureTestingModule

C After creating components

D It is optional and never needed

compileComponents compiles templates and must be called after configuration but before creating components.

Which array in TestBed configuration holds components you want to test?

A imports

B providers

C declarations

D exports

declarations is where you list components, directives, and pipes used in the test.

Explain how to set up TestBed to test an Angular component with a mock service.

Think about declarations, providers, compileComponents, and createComponent steps.

Describe the role of TestBed in Angular unit testing and why it is important.

Focus on how TestBed mimics Angular's environment for tests.