JAVA-1470 Move 10 articles to libraries-4 module

libraries-4/src/test/java/com/baeldung/pairs/VavrPairsUnitTest.java

@@ -0,0 +1,29 @@
+package com.baeldung.pairs;
+
+import io.vavr.Tuple2;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class VavrPairsUnitTest {
+    @Test
+    public void givenTuple_whenSetValue_shouldSucceed() {
+        String key = "Eleven";
+        double value = 11.0;
+        double newValue = 11.1;
+
+        Tuple2<String, Double> pair = new Tuple2<>(key, value);
+
+        pair = pair.update2(newValue);
+        Assert.assertTrue(newValue == pair._2());
+    }
+
+    @Test
+    public void givenPair_whenGetValue_shouldSucceed() {
+        String key = "Twelve";
+        double value = 12.0;
+
+        Tuple2<String, Double> pair = new Tuple2<>(key, value);
+
+        Assert.assertTrue(value == pair._2());
+    }
+}