There are some online resources like koolkareers.com (http://www.koolkareers.com/careers/category/cat-preparation/) which offers you an opportunity to test your general knowledge. There are some paid resources as well which conducts mock tests for CAT aspirants. Candidates need to register first to take the mock tests. Students can take these tests at their own convenience by sitting at home. You can also browse through the site Examzbuddy.com and take the online Mock CAT tests provided by the site. The duration of the tests offered is quite flexible. The site also offers analysis of the questions asked which is very helpful for the test takers.