[SOLVED] How do you run maven unit tests with hprof

How do you run maven unit tests with hprof

I'm trying to figure out why unit tests are taking seconds to run instead of milliseconds. This is a significant issue because over ~300 test classes, this results in 20 minutes. My hope is to use a performance analyzer (like java HPROF) with my maven unit tests. I would then analyze the hprof output on my own.

Solution

I added the below argline config to my surefire plugin block

<configuration>
    <forkMode>never</forkMode>
    <argLine>
        -agentlib:hprof=cpu=samples,lineno=y,depth=3,file=hprof.samples.txt
    </argLine>
    ...
<configuration>

You must not fork JVMs. All tests have to reuse the same jvm for this to work.

That generates an hprof file (see: https://docs.oracle.com/javase/7/docs/technotes/samples/hprof.html ). That gives you hints on what part of the code is slowing things down. In my case it was a combination of reuseFork=never and class loading.