Indirect Testing

A test class is supposed to test its counterpart in the production code. It starts to smell when a test class contains methods that actually perform tests on other objects (for example because there are references to them in the class-to-be-tested).

Reference

A. van Deursen, L. Moonen, A. Bergh, G. Kok, “Refactoring Test Code”, Technical Report, CWI, 2001.