Change default test class name suffix in Intellij IDEA

It's finally possible with the IntelliJ 2018.1:

With the IntelliJ IDEA 2018.1, you can customize a test class template and create a test class with Test as a prefix. Go to Preferences | Editor | Code Style | Java | Code Generation, and choose how the test class name should be generated. By default, the IDE creates a test class with the Test as a suffix.

Above is from this blog post