Static Cycles in Dependency Graphs

Two classes using each other constitute the simplest imaginable cycle in a dependency graph. The presence of many cycles in a system will lead to its lumping.

Related smells: Cyclically-dependent Modularization Dependency Cycles between Packages/Subsystems

Reference

M. Lippert, S. Roock, “Refactoring in Large Software Projects: Performing Complex Restructurings Successfully”. John Wiley and Sons, 2006.