title: Uncaught AssertionError: .empty was passed non-string primitive 1
body: <p>When I give this statement as below, an "Uncaught AssertionError: .empty was passed non-string primitive 1" is thrown
  expect(res.body.invoiceDetails.lineItems[0].invLineId).to.be.a('Number').and.not.to.be.empty;</p>