Add PN-Counter (#4974)

src/test/java/com/thealgorithms/datastructures/crdt/PNCounterTest.java

@@ -0,0 +1,54 @@
+package com.thealgorithms.datastructures.crdt;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+public class PNCounterTest {
+
+    @Test
+    public void testIncrement() {
+        PNCounter counter = new PNCounter(0, 3);
+        counter.increment();
+        assertEquals(1, counter.value());
+    }
+
+    @Test
+    public void testDecrement() {
+        PNCounter counter = new PNCounter(0, 3);
+        counter.decrement();
+        assertEquals(-1, counter.value());
+    }
+
+    @Test
+    public void testIncrementAndDecrement() {
+        PNCounter counter = new PNCounter(0, 3);
+        counter.increment();
+        counter.increment();
+        counter.decrement();
+        assertEquals(1, counter.value());
+    }
+
+    @Test
+    public void testCompare() {
+        PNCounter counter1 = new PNCounter(0, 3);
+        counter1.increment();
+        PNCounter counter2 = new PNCounter(1, 3);
+        assertTrue(counter1.compare(counter2));
+        counter2.increment();
+        assertTrue(counter2.compare(counter1));
+        counter1.decrement();
+        assertFalse(counter1.compare(counter2));
+    }
+
+    @Test
+    public void testMerge() {
+        PNCounter counter1 = new PNCounter(0, 3);
+        counter1.increment();
+        counter1.increment();
+        PNCounter counter2 = new PNCounter(1, 3);
+        counter2.increment();
+        counter1.merge(counter2);
+        assertEquals(3, counter1.value());
+    }
+}