DNA tests are a relatively new tool that can be used to investigate your ancestry. They're also known as genetic testing. This image shows a 233 and me DNA test in a box. The box contains all the materials you need to take the test. DNA tests use a small sample of your hair or blood to determine your genetic information. Are DNA tests reliable? There is no one answer to this question since different people have different opinions on whether or not they believe DNA tests are reliable. However, most experts agree that DNA tests provide accurate results in the majority of cases. How do DNA tests work? Generally, the test will collect a small sample of your hair or blood. The test will then use special techniques to identify specific genes in the sample.