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Untitled Masterpiece

Learn how to test pipes and directives in Angular.

Testing pipes

In this lesson, we will learn how to test a pipe. Previously, we learned that a pipe is a TypeScript class that implements the PipeTransform interface. It exposes a transform method, which is usually synchronous, which means it is straightforward to test. The list.pipe.ts file contains a pipe that converts a comma-separated string into a list:

import { Pipe, PipeTransform } from '@angular/core';
@Pipe({
  name: 'list'
})
export class ListPipe implements PipeTransform {
  transform(value: string): string[] {
    return value.split(',');
  }
}

Writing a test for it is simple. The only thing that we need to ...