.toBeInstanceOf (String) to buffer.toString () in Jest tests?

How can I use expect(str).toBeInstanceOf(String)

in a Jest assertion for a string that was created with Buffer#toString()

?

Or is the sure thing here expect(typeof str).toEqual('string')

instead?

More details:

This test case, using typeof

, passes:

it('should test a Buffer.toString() - typeof', () => {
  const buf = new Buffer('hello world');
  const str = buf.toString('hex');
  expect(buf).toBeInstanceOf(Buffer);
  expect(typeof str).toEqual('string');
  // expect(str).toBeInstanceOf(String);
});

      

        
        
        
      

    

However, this test case using .toBeInstanceOf()

fails:

it('should test a Buffer.toString()', () => {
  const buf = new Buffer('hello world');
  const str = buf.toString('hex');
  expect(buf).toBeInstanceOf(Buffer);
  // expect(typeof str).toEqual('string');
  expect(str).toBeInstanceOf(String);
});

      

        
        
        
      

    

Here's the Jest displayed for it:

 FAIL  ./buffer.jest.js
  ● should test a Buffer.toString()

    expect(value).toBeInstanceOf(constructor)

    Expected value to be an instance of:
      "String"
    Received:
      "68656c6c6f20776f726c64"
    Constructor:
      "String"

      at Object.<anonymous>.it (password.jest.js:11:15)
      at Promise.resolve.then.el (node_modules/p-map/index.js:42:16)
      at process._tickCallback (internal/process/next_tick.js:109:7)