test-utils.ts

import { resolve } from 'path';
import { TSESLint } from '@typescript-eslint/experimental-utils';

const DEFAULT_TEST_CASE_CONFIG = {
  filename: 'MyComponent.test.js',
};

class TestingLibraryRuleTester extends TSESLint.RuleTester {
  run<TMessageIds extends string, TOptions extends Readonly<unknown[]>>(
    ruleName: string,
    rule: TSESLint.RuleModule<TMessageIds, TOptions>,
    tests: TSESLint.RunTests<TMessageIds, TOptions>
  ): void {
    const { valid, invalid } = tests;

    const finalValid = valid.map((testCase) => {
      if (typeof testCase === 'string') {
        return {
          ...DEFAULT_TEST_CASE_CONFIG,
          code: testCase,
        };
      }

      return { ...DEFAULT_TEST_CASE_CONFIG, ...testCase };
    });
    const finalInvalid = invalid.map((testCase) => ({
      ...DEFAULT_TEST_CASE_CONFIG,
      ...testCase,
    }));

    super.run(ruleName, rule, { valid: finalValid, invalid: finalInvalid });
  }
}

export const createRuleTester = (
  parserOptions: Partial<TSESLint.ParserOptions> = {}
): TSESLint.RuleTester => {
  return new TestingLibraryRuleTester({
    parser: resolve('./node_modules/@typescript-eslint/parser'),
    parserOptions: {
      ecmaVersion: 2018,
      sourceType: 'module',
      ecmaFeatures: {
        jsx: true,
      },
      ...parserOptions,
    },
  });
};