diff -r aa70afac4eca -r 3a1f262311cf rt/emul/compacttest/src/test/java/org/apidesign/bck2brwsr/tck/ConcurrentTest.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rt/emul/compacttest/src/test/java/org/apidesign/bck2brwsr/tck/ConcurrentTest.java	Wed Nov 19 19:32:00 2014 +0100
@@ -0,0 +1,40 @@
+/**
+ * Back 2 Browser Bytecode Translator
+ * Copyright (C) 2012 Jaroslav Tulach <jaroslav.tulach@apidesign.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. Look for COPYING file in the top folder.
+ * If not, see http://opensource.org/licenses/GPL-2.0.
+ */
+package org.apidesign.bck2brwsr.tck;
+
+import java.util.concurrent.ConcurrentHashMap;
+import org.apidesign.bck2brwsr.vmtest.Compare;
+import org.apidesign.bck2brwsr.vmtest.VMTest;
+import org.testng.annotations.Factory;
+
+/**
+ *
+ * @author Jaroslav Tulach <jtulach@netbeans.org>
+ */
+public class ConcurrentTest {
+    @Compare public String mapIfAbsent() {
+        ConcurrentHashMap<String,String> m = new ConcurrentHashMap<>();
+        m.putIfAbsent("Ahoj", "Jardo");
+        m.putIfAbsent("Ahoj", "Dardo");
+        return m.get("Ahoj");
+    }
+    
+    @Factory public static Object[] create() {
+        return VMTest.create(ConcurrentTest.class);
+    }
+}