./gradlew -q text

For e.g. 10 days:

./gradlew run --args 10

You should make sure the gradle commands shown above work when you execute them in a terminal before trying to use TextTest (see below).

There are instructions in the TextTest Readme for setting up TextTest. What's unusual for the Java version is there are two executables listed in config.gr for Java. One uses Gradle wrapped in a python script, the other relies on your CLASSPATH being set correctly in environment.gr.