router.get("/url", function(req, res){
  let options = { url: "http//some-api-en-point",
    method: "GET",
    resolveWithFullResponse: true
  };
  rp(options)
  .then(function(response) {
    if(response.statusCode == 200){
      res.send({"data":response.data})
    } else {
      res.status(404).json("data":"NOT FOUND");
    }
  })
  .catch(err => () => {
    res.send(err);
  })
});

{
  "id": "3f3e2b23e96c5250441d4be2340010ed",
  "email": "let@example.com",
  "status": "1"
}

describe('TEST: /URL', () => {

  it('it should return Status 200', (done) => {
    chai.request(app)
      .get('/url')
      .end((err, res) => {
        sinon.stub(rp, 'Request').resolves({statusCode:200});
        expect(res).to.have.status(200);
        done();
      });
  });
});