Test code, just like any other code we write, erodes when frequently changed. As such, refactoring, which has been shown to impact maintainability and comprehensibility, can be part of a solution to counter this erosion. We propose a metric-based heuristical approach, which allows to rank occurrences of so-called test smells (i.e. symptoms of poorly designed tests) according to their relative significance. This ranking can subsequently be used to start refactoring. Through an open-source case study, ArgoUML, we demonstrate that we are able to identify those test cases who violate unit test criteria.