The virtual mock tests deliberately have background noises running, which includes coughing, whilst you take the test papers. This is the ‘realistic exam hall experience’ that is advertised on the virtual mock exams information page:
The real 11+ exams will not be held in completely quiet rooms. In any exam you will have noises around you which can sometimes be quite distracting, Therefore, it is best if you practise taking a mock test with the same.
I hope that you did well 🙂