You’re very welcome!
This is a problem that affects the Santulator GUI test during the Gradle build on Windows. I’m not sure what causes it but it doesn’t happen on Mac or Linux. I’ve created an issue for it here. My guess is it’s either a problem with TestFX on Windows or is something about the way I use TestFX. If you have any more information, please do add it to the issue.
Interestingly, the problem only seems to affect the “Headless” GUI test mode. If you run the same build but add the option -PnoHeadless to the command line, you’ll allow the test to run in a normal window and you can watch the robot clicking the buttons (don’t be alarmed by your display being temporarily taken over!). You might need to minimise your cmd window but you should find that option allows the build to run. Alternatively, to skip the GUI test altogether, add -PskipGuiTests to your Gradle command line.