The CITB HS&E test is given at the end of the day-long course. It is composed of 50 multiple-choice questions directly related to safety and health issues raised during the course. In order to pass the test and receive certification you must answer 90% of the questions correctly (45 out of 50).
Should you fail you will need to wait 48 hours before you are eligible to retake the test. However, you will need to register again and pay the testing fee again as well. Remember, if you hope to work for a reputable construction company you will need to be certified.