GOSSIP-63 Added CRDT G-Counter implementation

src/test/java/org/apache/gossip/crdt/GrowOnlyCounterTest.java

@@ -0,0 +1,54 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.gossip.crdt;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class GrowOnlyCounterTest {
+  
+  @Test
+  public void mergeTest() {
+    
+    Map<String, Long> node1Counter = new HashMap<>();
+    node1Counter.put("1", 3L);
+    Map<String, Long> node2Counter = new HashMap<>();
+    node2Counter.put("2", 1L);
+    Map<String, Long> node3Counter = new HashMap<>();
+    node3Counter.put("3", 2L);
+    
+    GrowOnlyCounter gCounter1 = new GrowOnlyCounter(node1Counter);
+    GrowOnlyCounter gCounter2 = new GrowOnlyCounter(node2Counter);
+    GrowOnlyCounter gCounter3 = new GrowOnlyCounter(node3Counter);
+    
+    // After node 2 receive from node 1
+    gCounter2 = gCounter2.merge(gCounter1);
+    Assert.assertEquals(4, (long) gCounter2.value());
+    
+    // After node 3 receive from node 1
+    gCounter3 = gCounter3.merge(gCounter1);
+    Assert.assertEquals(5, (long) gCounter3.value());
+    
+    // After node 3 receive from node 2
+    gCounter3 = gCounter3.merge(gCounter2);
+    Assert.assertEquals(6, (long) gCounter3.value());
+  }
+}