diff -r 000000000000 -r 8e220093e4bf samples/singletons/test/org/apidesign/singletons/usage/MainTest.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/samples/singletons/test/org/apidesign/singletons/usage/MainTest.java	Wed Jan 27 18:30:57 2010 +0100
@@ -0,0 +1,37 @@
+package org.apidesign.singletons.usage;
+
+import org.apidesign.singletons.api.DialogDisplayer;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import org.netbeans.junit.MockServices;
+import static org.junit.Assert.*;
+
+public class MainTest {
+
+    public MainTest() {
+    }
+
+    @BeforeClass
+    public static void setUpClass() throws Exception {
+        MockServices.setServices(MockDialogDisplayer.class);
+    }
+
+    @Test
+    public void testMainAsksAQuestion() {
+        assertNull("No question asked yet", MockDialogDisplayer.askedQuery);
+        Main.main(new String[0]);
+        assertNotNull("main code asked our Mock displayer", MockDialogDisplayer.askedQuery);
+    }
+
+    public static final class MockDialogDisplayer extends DialogDisplayer {
+        static String askedQuery;
+        
+        @Override
+        public boolean yesOrNo(String query) {
+            askedQuery = query;
+            return false;
+        }
+
+    }
+}
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