Unit testing the components

Components form the most important building block of any Angular app. Thus, it is of utmost importance to write good unit tests for components, and ensure maximum possible code coverage.

Angular testing utilities will be used for writing unit tests for components. In this regard, concepts discussed earlier such as TestBed, componentFixture, and DebugElement will be used to create the test environment for the components to be tested. In this section, we will take different sample components starting from the most trivial ones to the most complex components, and learn about writing and running unit tests for these components.

Unit testing a component with an external template

As one sets up the Angular app, one can find the most trivial component, AppComponent, in the root folder (src/app) with an external template used. Note that there are no dependencies, such as services. The following is the code for AppComponent saved as the file app.component.ts:

    import {Component...