matchers.md

Matchers

The cli-testing-library provides a set of custom jest matchers that you can use to extend jest. These will make your tests more declarative, clear to read and to maintain.

Table of Contents

• Usage
  • With TypeScript
• Custom matchers
  • toBeInTheConsole
    • Examples
  • toHaveErrorMessage
    • Examples

Usage

Import cli-testing-library/extend-expect once (for instance in your tests setup file) and you're good to go:

// In your own jest-setup.js (or any other name)
import 'cli-testing-library/extend-expect'

// In jest.config.js add (if you haven't already)
setupFilesAfterEnv: ['<rootDir>/jest-setup.js']

With TypeScript

If you're using TypeScript, make sure your setup file is a .ts and not a .js to include the necessary types.

You will also need to include your setup file in your tsconfig.json if you haven't already:

  // In tsconfig.json
  "include": [
    ...
    "./jest-setup.ts"
  ],

Custom matchers

toBeInTheConsole

toBeInTheConsole()

This allows you to assert whether an instance is present or not. Useful when combined with queries (such as getByText or getByError) that return the TestInstance

Examples

Input your name:

expect(getByText(instance, 'Input your name:')).toBeInTheConsole()

---

toHaveErrorMessage

toHaveErrorMessage(text: string | RegExp)

This allows you to check whether the given instance has an stderr message or not.

Whitespace is normalized.

When a string argument is passed through, it will perform a whole case-sensitive match to the error message text.

To perform a case-insensitive match, you can use a RegExp with the /i modifier.

To perform a partial match, you can pass a RegExp.

Examples

File not found in output

expect(instance).toHaveErrorMessage('File not found in output')