Just like its predecessor, Angular 1, Angular has been designed with testability as a primary goal.

When we talk about testing in Angular we are usually talking about two different types of testing:

Unit Testing
This is sometimes also called Isolated testing. It’s the practice of testing small isolated pieces of code. If your test uses some external resource, like the network or a database, it’s not a unit test.

Functional Testing
This is defined as the testing of the complete functionality of an application. In practice with web apps, this means interacting with your application as it’s running in a browser just like a user would interact with it in real life, i.e. via clicks on a page.

This is also called End to End or E2E testing.