Hey there

This is a common confusion but let me tell you that you should start your mock test untill you have completed your syllabus atleast once then you should start giving your mock test and find your weak portions where you have not done well and focus on that portion.

Check about cat

https://www.google.com/url?sa=t&source=web&rct=j&url=https://bschool.careers360.com/exams/cat&ved=2ahUKEwjJtP6Ij9riAhWp8HMBHXcCAbMQFjAAegQIAhAB&usg=AOvVaw0WGtiQe_DqSNQSEEbxSdmI

Good luck