Estrangement between Classes: Test Coverage-Based Assessment of Coupling Strength between Pairs of Classes

This work discusses a new metric, Estrangement Between Classes (EBC), that is derived by executing tests. This metric is based on the statement coverage of tests and provides assessment of the strength of associations between classes. We demonstrate with an illustrative example of the popular Apache Email component that this new metric can provide additional information in reverse engineered class diagrams by highlighting missing associations in these diagrams, the strength of existing associations and utility classes. It can also be effective in indicating the important design elements in cases of over-engineered or dead code. The proposed metric can be potentially used in the context of agile methods of software development during refactoring and program maintenance as comprehension aid. Since EBC is based on tests, no additional effort is required by developers who follow the Test-Driven approach or generally develop tests.