According to the Wisconsin Nurse Aide Registry, an individual must pass both parts of the CNA exam within one year of CNA program completion in order to obtain certification. If you did not take the exam, or failed to pass it within one year of graduation, you must complete another training class to qualify again for testing. The Wisconsin Department of Health Services advises that you should contact the American Red Cross toll-free at 866-257-5424 to learn more about nurse aide testing requirements.