more-jest

TypeScript matchers and utilities for Jest

more-jest is a TypeScript library providing additional matchers for Jest as well as types and utilities for creating custom matchers; consequently, it serves as the fundamental building block for dedicated libraries like more-jest-io.

Installation

npm install @giancosta86/more-jest

or

yarn add @giancosta86/more-jest

The public API entirely resides in the root package index, so one shouldn't reference specific modules from TypeScript code.

Global matchers

In order to be able to access the custom matchers provided by this library within any test file in your project, please follow these steps:

1. Create a declaration file (for example, global.d.ts) in the root directory of your project, containing the following line:

   import "@giancosta86/more-jest";

2. In the jest.config.js configuration file, add an entry to the setupFilesAfterEnv array field:

   module.exports = {
     setupFilesAfterEnv: ["@giancosta86/more-jest/dist/all"]
   };

Matchers

• toBeTrimmed(): ensures that the received string contains neither leading nor trailing spaces:

  expect("DODO").toBeTrimmed(); //OK
  
  expect("   DODO").toBeTrimmed(); //FAILURE!
  
  expect("DODO   ").toBeTrimmed(); //FAILURE!

Utilities

more-jest provides:

• the MatcherResult readonly type - which should be the return type of custom matcher handlers

• the failMatcherIf() function, designed to be called as the return value of custom matcher handlers

• the matcherSuccess constant - to be returned by more sophisticated matcher handlers

Further references

• more-jest-io - TypeScript I/O matchers and utilities for Jest