Giving down mock tests helps one a lot as you are able to channelize yourself in a better way like you can understand where exactly do you stand. What more things you've to work upon and what things you've already mastered. You also learn to manage time through this.

Here is the link for sample papers and mock tests of GPAT exam..

https://pharmacy.careers360.com/articles/gpat-question-papers

Best wishes. Thank-you.