expect.stringMatching(string | regexp) matches the received value if it is a string that matches the expected string or regular expression.

You can use it instead of a literal value:

in toEqual or toBeCalledWith
to match an element in arrayContaining
to match a property in objectContaining or toMatchObject

This example also shows how you can nest multiple asymmetric matchers, with expect.stringMatching inside the expect.arrayContaining.

describe('stringMatching in arrayContaining', () => {
  const expected = [
    expect.stringMatching(/^Alic/),
    expect.stringMatching(/^[BR]ob/),
  ];
  it('matches even if received contains additional elements', () => {
    expect(['Alicia', 'Roberto', 'Evelina']).toEqual(
      expect.arrayContaining(expected),
    );
  });
  it('does not match if received does not contain expected elements', () => {
    expect(['Roberto', 'Evelina']).not.toEqual(
      expect.arrayContaining(expected),
    );
  });
});