STRUCTURAL COUPLING Structural coupling is one of the strongest, and most insidious, forms of test coupling. Imagine a test suite that has a test class for every production class, and a set of test methods for every production method. Such a test suite is deeply coupled to the structure of the application. When one of those production methods or classes changes, a large number of tests must change as well. Consequently, the tests are fragile, and they make the production code rigid.
