While writing this post about the Lucene Codec API I noticed something strange when running the tests with Gradle. When experimenting with a library feature most of the times I write unit tests that validate my expectations. This is a habit I learned from Lucene in Action and can also be useful in real world scenarios, e.g. to make sure that nothing breaks when you update a library.
OK, what happened? This time I did not only want to have the test result but also ran the test for a side effect, I wanted a Lucene index to be written to the /tmp directory to manually have a look at it. This worked fine for the first time, but not afterwards, e.g. after my machine was rebooted and the directory cleared.
It turns out that the Gradle developers know that a test shouldn't be used to execute stuff. So once the test is run successfully it is just not run again until its input changes! Though this bit me this time this is a really nice feature to speed up your builds. And if you really need to execute the tests, you can always run
gradle cleanTest test.