A few days ago we changed nexus integration tests to use an embedded version of nexus instead of using a forked VM. Before every test Nexus is started and then stopped again after the test completes. This is done once for each test class (Junit: @BeforeClass=start nexus, @AfterClass=stop nexus).
During the first run we noticed some problems.Each time Nexus started, VM would use an additional 45Mb of memory. Soon we realized that our embedder was not working right. Stopping Nexus was not removing it from memory.
Setting all fields to null after stopping helped somewhat. But now instead of 45Mb of leak we were getting 40Mb, which was still too much when we had more then 200 tests to run. It was time to profile our tests.
At Sonatype we use yourkit for profiling, so I will demonstrate how to use yourkit to profile tests executed by maven. You should be able to use the same principle with any other profile tool. Continue reading