The effectiveness of the test sets is usually found by the fault coverage. This is the percentage of detectable faults in the circuit under test that are detected by the test set. The level of fault coverage is desirable, but rarely attainable in most practical circuits. The fault coverage refers to the percentage of some type of fault that can be detected during the test of any engineered system. High fault coverage is particularly valuable during manufacturing test. Testing is a process is to find the fault. And to improve the effectiveness of test set fault coverage is been carried out. The main objective is to improve the fault coverage of the transition delay faults. A new type of detection conditions for delay faults, referred to as hazard-based detection conditions, to enhance the coverage of delay faults using the standard scan test application methods. Some delay faults, including irredundant faults, may be undetectable under the conventional detection conditions. These faults may be detectable under the hazard-based detection conditions. Some delay faults, including irredundant faults, may be undetectable under the conventional detection conditions. These faults may be detectable under the hazard-based detection conditions. The use of hazard-based detection conditions thus improves the delay fault coverage achievable for a circuit.