For 2 reasons: 1) that code (mainly the spy one) was not being used or needed on all the test cases and 2) because for the new tests we have to set the set the call duration before the _disconnect() function is called to verify that the code is behaving properly. I mean this:
```javascript
var totalCallDuration = '12:34';
        subject.node.querySelector('.duration span').textContent =
          totalCallDuration;
        mockCall._disconnect();
```