The GS Simulator Tests along with CSAT Simulator Tests and All India Open Mock Tests make sure that you have undergone different quality/difficulty and pattern for the Prelims paper by simulating the past 5 - 6 years of UPSC papers.
The simulators help to make the Prelims exam predictable for you. They provide for timely assessment and gauging of the competition. While Knowledge Base can be developed by reading standard books, the other aspect - problem-solving skills, elimination skills and decision making comes with practising previous years’ papers and solving high-quality simulator Test papers.