core tests should run headless

Signed-off-by: Florian Thienel <florian@thienel.org>
diff --git a/org.eclipse.vex.core.tests/src/org/eclipse/vex/core/tests/VEXCoreTestPlugin.java b/org.eclipse.vex.core.tests/src/org/eclipse/vex/core/tests/VEXCoreTestPlugin.java
index 4d45e70..d61de3e 100644
--- a/org.eclipse.vex.core.tests/src/org/eclipse/vex/core/tests/VEXCoreTestPlugin.java
+++ b/org.eclipse.vex.core.tests/src/org/eclipse/vex/core/tests/VEXCoreTestPlugin.java
@@ -1,12 +1,12 @@
 package org.eclipse.vex.core.tests;
 
-import org.eclipse.ui.plugin.AbstractUIPlugin;
+import org.eclipse.core.runtime.Plugin;
 import org.osgi.framework.BundleContext;
 
 /**
  * The activator class controls the plug-in life cycle
  */
-public class VEXCoreTestPlugin extends AbstractUIPlugin {
+public class VEXCoreTestPlugin extends Plugin {
 
 	// The plug-in ID
 	public static final String PLUGIN_ID = "org.eclipse.vex.core.tests";