@Override
      public Object call() throws Exception {
        final Region r = getCache().getRegion(regionName);
        assertNull(r.putIfAbsent("key0", "value"));
        assertTrue(r.containsKey("key0"));
        assertNull(r.putIfAbsent("key2", "value2"));
        assertTrue(r.containsKey("key2"));
        return null;
      }
Partitioned Region test for bug #42195: putIfAbsent from client does not put old value in local
cache
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/ConcurrentMapOpsDUnitTest.java