system tester in simple language is a tool to check the profitability of your technical analysis before even trading. In the system tester you need to define why you will buy, why will you exit and vice versa for short.
based on these rules defined system tester will do a test on the historical data and give you the results of your trading strategy. for eg if i want to buy a stock if it crosses the 13 ema then in the enter long field i will write cross(c,mov(c,13,e) and in enter short cross(mov(c,13,e),c) so once you run the system tester you will get results like no. of trades done, profit on long trades profit on short trades and a host of other stats which help us understand the system better.
a systems accuracy has to be tested on various factors like testing the same system on various scrips, the long and short profit ratio, no of wining trades viz total no. of trades and a host of others
regds
raminder