Jest自定义匹配器:在匹配器内部未定义"this“

expect.extend({
  toBeDivisibleBy(received, divisor) {
    const pass = received % divisor === 0;
    if (pass) {
      return {
        message: () =>
          `expected ${received} not to be divisible by ${divisor}`,
        pass: true,
      };
    } else {
      return {
        message: () =>
          `expected ${received} to be divisible by ${divisor}`,
        pass: false,
      };
    }
  },
});

test('16 is divisible by 4', () => {
  expect(16).toBeDivisibleBy(4);
});

test('25 is not divisible by 3', () => {
  expect(25).not.toBeDivisibleBy(3);
});