Use a truely unknown Event when testing for unknown events

At some point in the future, we might want to allow triggering on
TopicChangedEvents. Then we should not have to think why the test for
unknown events failed. Hence, we use a custom, truely unknown Event to
test handling of unknown events.

Change-Id: I01153b75245805df30cd188b14ab439131c22feb

src/test/java/com/googlesource/gerrit/plugins/its/base/its/ItsConfigTest.java

diff --git a/src/test/java/com/googlesource/gerrit/plugins/its/base/its/ItsConfigTest.java b/src/test/java/com/googlesource/gerrit/plugins/its/base/its/ItsConfigTest.java
index 22bc4ee..6be9652 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/its/base/its/ItsConfigTest.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/its/base/its/ItsConfigTest.java
@@ -30,9 +30,9 @@
 import com.google.gerrit.server.events.ChangeRestoredEvent;
 import com.google.gerrit.server.events.CommentAddedEvent;
 import com.google.gerrit.server.events.DraftPublishedEvent;
+import com.google.gerrit.server.events.Event;
 import com.google.gerrit.server.events.PatchSetCreatedEvent;
 import com.google.gerrit.server.events.RefUpdatedEvent;
-import com.google.gerrit.server.events.TopicChangedEvent;
 import com.google.gerrit.server.project.ProjectCache;
 import com.google.gerrit.server.project.ProjectState;
 import com.google.inject.Guice;
@@ -474,8 +474,8 @@
     assertTrue(itsConfig.isEnabled(event));
   }
 
-  public void testIsIgnoredTopicChangedEvent() {
-    TopicChangedEvent event = new TopicChangedEvent();
+  public void testIsEnabledUnknownEvent() {
+    Event event = new Event("foo") {};
 
     ItsConfig itsConfig = createItsConfig();