You should practice on real tests because:
First, these extracted from IELTS bank source; therefore, you are in all probability to take these tests in your real examinations. This statement can be proven by the attached index indicating the dates these tests were taken.
Second, when practicing this book, you can evaluate at the nearest possibility how difficult the IELTS Listening Part is in the real exam, and what the top most common traps are. Another important point is that these real tests are much more tricky and difficult than the ones in the IELTS Cambridge books.