Kieker is a framework for continuous monitoring and dynamic analysis of distributed software systems. Being designed for continuous operation, it induces only a low overhead. The TraceAnalysis tool allows to analyze and visualize trace information.
JRET (Java Reverse-Engineering Tool) is a program that is capable of reconstructing sequence diagrams from JUnit testsuites through dynamic analysis. It is written in Java/AspectJ and provides a GUI as well as command-line possibilities.
JUnitMetrics is a tool that enables to measure basic JUnit and Cactus tests metrics (like number of tests, assertions, number of executed assertions). It is great, complementary solution to code coverage tools and mutation testers.