Here’s a list of all the features that you can expect from JUnit Pioneer. For some of them you need to be quite familiar with JUnit 5, so make sure to read its user guide or this article series.

@DefaultLocale and @DefaultTimeZone
JUnit Jupiter extensions to change the values returned from Locale.getDefault() and TimeZone.getDefault()
TempDirectory
JUnit Jupiter extension to create and clean up a temporary directory.
Vintage @Test
A drop-in replacement for JUnit 4's @Test annotation, including expected and timeout

To start using JUnit Pioneer, determine the latest version (e.g. on Maven Central) and add org.junit-pioneer : junit-pioneer as a test dependency.