Function toBeInstanceOf

packages/expect/src/matchers.ts:295–345

(received: any, expected: Function)

  },

  toBeInstanceOf(received: any, expected: Function) {
    const matcherName = 'toBeInstanceOf';
    const options: MatcherHintOptions = {
      isNot: this.isNot,
      promise: this.promise,
    };

    if (typeof expected !== 'function') {
      throw new TypeError(
        matcherErrorMessage(
          matcherHint(matcherName, undefined, undefined, options),
          `${EXPECTED_COLOR('expected')} value must be a function`,
          printWithType('Expected', expected, printExpected),
        ),
      );
    }

    const pass = received instanceof expected;

    const message = pass
      ? () =>
          // eslint-disable-next-line prefer-template
          matcherHint(matcherName, undefined, undefined, options) +
          '\n\n' +
          printExpectedConstructorNameNot('Expected constructor', expected) +
          (typeof received.constructor === 'function' &&
          received.constructor !== expected
            ? printReceivedConstructorNameNot(
                'Received constructor',
                received.constructor,
                expected,
              )
            : '')
      : () =>
          // eslint-disable-next-line prefer-template
          matcherHint(matcherName, undefined, undefined, options) +
          '\n\n' +
          printExpectedConstructorName('Expected constructor', expected) +
          (isPrimitive(received) || Object.getPrototypeOf(received) === null
            ? `\nReceived value has no prototype\nReceived value: ${printReceived(
                received,
              )}`
            : typeof received.constructor === 'function'
              ? printReceivedConstructorName(
                  'Received constructor',
                  received.constructor,
                )
              : `\nReceived value: ${printReceived(received)}`);

    return {message, pass};
  },

  toBeLessThan(received: number | bigint, expected: number | bigint) {
    const matcherName = 'toBeLessThan';