The feedback that I have received suggests that my exams are difficult.
You mentioned that you have already completed an exam study guide. I believe that my mock exams are most effective when the single topic exams are used as you work through an exam study guide chapter-by-chapter. In other words, the single topic exams can be used to supplement any study guide.
I have noticed that the developers of some the commercial exams will advertise the fact that their questions are designed to closely resemble the questions on the real exam. In contrast, the majority of my exam tends to be a collection of complete programs that can be compiled and tested. For that reason, my exam is unique. I believe that it provides a great learning experience. However, it probably does not provide the best tool for predicting your performance on the real exam.
I encourage people to start using my single topic exams at the very beginning of the study process. Since my exam is designed to provide a learning experience I suggest working through a single topic exam as soon as you complete a related chapter in any study guide. You can ignore the score on my exam and just focus on learning what you can as you work through each question. After you have completed my single topic exam, then try the exam at the end of the chapter in the study guide. My expectation is that you will do very well on the exam in your book.
At the end of the study process you should
search for mock exams that are designed to closely resemble the real exam. The Marcus Green exams are a good example.
Another reason for suggesting the use of other mock exams is the fact that my exam is not yet complete. For example, I have not yet started working on the garbage collection topic and the thread
exam is only now being developed. A beta version is available for threads, but I really should have called it an alpha version since I have not yet covered all of the material.
Please don't allow yourself to be discouraged by your score on my exam. My exam should be viewed as a learning experience and not a measurement tool.