Quality Assurance and Testing with Chai - failing the overall test but all of the individual test cases are getting passed

Quality Assurance and Testing with Chai - Run Functional Tests on an API Response using Chai-HTTP III - PUT method

I am unable to pass the overall test but all of the individual test cases are getting passed.

Here is my code:

   test('send {surname: "Colombo"}',  function(done){
       
       // we setup the request for you...
       chai.request(server)
        .put('/travellers')
        /** send {surname: 'Colombo'} here **/
        // .send({...})
        .end(function(err, res){
          
          /** your tests here **/
          assert.equal(res.status, 200);
          assert.equal(res.type, 'application/json');
          assert.equal(res.body.name, 'Cristoforo');
          assert.equal(res.body.surname, 'Colombo');
          
          done(); // Never forget the 'done()' callback...
        });
      });

Getting this output:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36.

Link to the challenge: