Shadow pattern: A new design pattern for testing

Introduced in this paper is a new design pattern: a shadow for testing object-oriented programs. This pattern creates a shadow object for each object using it. By using this pattern, no additional test driver or test stub is needed. Thus, the pattern allows test scripts to be embedded in the program seamlessly. During testing, the test case can either call the shadow object as test stub or call the actual application code. The test script can make its decision at runtime to select which one to use. These ideas are illustrated in module testing and integration testing.