QUnit

I read this web-page. It contains code example:

1. QUnit.test( "step test", function( assert ) {
2.   obj.start = function() {
3.     assert.step('start');
4.   };
5.   obj.middle = function() {
6.     assert.step('middle');
7.   };
8.   obj.end = function() {
9.     assert.step('end');
10.   };
11.   return obj.process().then(function() {
12.     assert.verifySteps(['start', 'middle', 'end']);
13.   });
14. });

What is obj in this code example? 

I don't understand how to use `assert.verifySteps` method. This is my attempt:

1. QUnit.test( "step test", function( assert ) {
2.   let obj = {};
3.   obj.start = function() {
4.     assert.step('start');
5.   };
6.   obj.middle = function() {
7.     assert.step('middle');
8.   };
9.   obj.end = function() {
10.     assert.step('end');
11.   };
12.   return assert.verifySteps.bind(obj)(['start', 'middle', 'end']);
13. });

Thank you.