As circuit design is a complex and time consuming task so designers take assistance of optimization tools resulting in a better design in reduced time compared to the intuitive approach. With increase in circuit density, the number of interconnections increases exponentially and so are the chances of manufacturing defects or faults. Evolutionary algorithms (EA) have the ability to solve complex optimization problems related to circuit design. A DE based fault simulator is proposed which searches for test vectors with maximum fault coverage with in a large solution space. It also helps in compacting the test vectors set employed to cover all the faults occurred, by selecting the test vectors with maximum number of undetected faults only.