A method and system for dynamically invoking and/or checking conditions of a computer test program. Test cases that verify class/component functionality are automatically created from the DbC contracts. When the classes/components that contain DbC contracts are added to the system, the invention automatically verifies whether the system uses them correctly. The information in the contract comments is used to generate more comprehensive and better quality test cases. In one embodiment, a code's specification information is analyzed and a class with extra bytecodes that describe how the class is supposed to work and be used is generated. Next, the instrumented class is integrated into the system, and the system is run. The system is monitored as it runs and contract violations are automatically detected.