Jest custom `toMatch` with string normalization

custom-matchers.ts

import { matcherHint, printReceived, printExpected } from 'jest-matcher-utils';

const matches = (received: string, expected: string | RegExp) =>
  typeof expected === 'string'
    ? received.includes(expected)
    : expected.test(received);

const normalize = (text: string) => text.replace(/\s+/g, ' ').trim();

expect.extend({
  toMatchNormalized(received: string, expected: string | RegExp) {
    const isString = typeof expected === 'string';
    const exp = isString ? normalize(expected as string) : expected;
    const rec = normalize(received);
    const checkEmptyStrings = exp !== '' && rec === '';

    return {
      pass: !checkEmptyStrings && matches(rec, exp),
      message: () => {
        const to = this.isNot ? 'not ' : '';
        const typeExpected = isString ? 'substring' : 'pattern';
        const labelExpected = `Expected ${typeExpected}: ${to}`;
        const labelReceived = `Received string: ${' '.repeat(
          typeExpected.length - 6 + to.length
        )}`;

        return [
          matcherHint('toMatchNormalized'),
          `\n\n`,
          `${labelExpected}${printExpected(expected)}\n`,
          `${labelReceived}${printReceived(received)}`,
        ].join('');
      },
    };
  },
});