CogAT® sample test papers are not generally available but you can buy CoGAT test preparation books from large bookstores or online book retailers to help you prepare for your coming exam. CoGAT tests are normally taken by children in primary schools so if you (or your child) is at primary school, ask the school teachers for advice about CoGAT preparation.
CogAT (sometimes also referred to as CAT) stands for Cognitive Abilities Test and is a standard set of tests for verbal, quantitative and nonverbal reasoning skills. These tests are used to assess a child’s potential to succeed academically because they measure problem solving ability and reasoning skills rather than memorized knowledge.
CogAT is a registered trademark and the actual tests are published by Riverside Publishing. Riverside Publishing do not provide sample test papers or publish past papers so be wary of websites which appear to be selling them as they will, most likely, be fake.
Riverside Publishing do issue an example test to teachers which can be used only to help familiarize students with the exam question formats, but not the actual tested material. You cannot buy these but your school teacher should be able to get a copy to show you.
The whole premise of the tests is based on ability rather than learning so the best preparation for the exam is to work on your critical thinking skills. Search for "thinking skills” or "CoGAT skills” in online bookstores to see what material is available but make sure you choose books for the same grade as your exam.