[INFO] --- tycho-surefire-plugin:1.3.0-SNAPSHOT:test (default-test) @ org.eclipse.ui.ide.application.tests --- ...application, org.eclipse.tycho.surefire.osgibooter.headlesstest...
Which shows that the application run to test this plugin is headless (no workbench).
If you need UI for your test, you need to tweak the configuration of Maven surefire plugin so the workbench is created: https://www.eclipse.org/tycho/sitedocs/tycho-surefire/tycho-surefire-plugin/test-mojo.html#useUIHarness
HTH