@typescript-eslint/rule-tester

What is @typescript-eslint/rule-tester?

@typescript-eslint/rule-tester is a utility package designed to help developers test custom ESLint rules for TypeScript code. It provides a framework for writing unit tests for ESLint rules, ensuring that they behave as expected when applied to TypeScript code.

What are @typescript-eslint/rule-tester's main functionalities?

Testing ESLint Rules

This feature allows you to test custom ESLint rules by providing valid and invalid code samples. The RuleTester runs the rule against these samples and checks if the expected errors are reported.

const { RuleTester } = require('@typescript-eslint/rule-tester');
const rule = require('path/to/your/custom-rule');

const ruleTester = new RuleTester({
  parser: '@typescript-eslint/parser',
});

ruleTester.run('your-rule-name', rule, {
  valid: [
    {
      code: 'const x: number = 42;',
    },
  ],
  invalid: [
    {
      code: 'const x: string = 42;',
      errors: [{ messageId: 'expectedNumber' }],
    },
  ],
});

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README

@typescript-eslint/rule-tester

Tooling to test ESLint rules

👉 See https://typescript-eslint.io/architecture/rule-tester for documentation on this package.