toBeISODate Jest matcher

setupJest.js

expect.extend({
  toBeISODate(received) {
    // This regexp checks for formatting
    if (
      !/\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}.\d{3}Z/.test(received)
    ) {
      return {
        pass: false,
        message: `Expected ${received} to be a valid ISO date string`,
      };
    }
    
    // This checks if JS can correctly parse it
    const d = new Date(received);
    return d.toISOString() === received
      ? {
          pass: true,
          message: 'Expected ${received} not to be a valid ISO date string',
        }
      : {
          pass: false,
          message: `Expected ${received} to be a valid ISO date string`,
        };
  },
});