Added test cases to OddEvenSort. (#3768)

* Add testcase to CocktailShakerSort Algorithm

* fixed method name to lowerCamelCase

* Added test cases to OddEvenSortTest

src/test/java/com/thealgorithms/sorts/OddEvenSortTest.java

@@ -0,0 +1,39 @@
+package com.thealgorithms.sorts;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * @author Tabbygray (https://github.com/Tabbygray)
+ * @see OddEvenSort
+ */
+
+public class OddEvenSortTest {
+    private OddEvenSort oddEvenSort = new OddEvenSort();
+
+    @Test
+    public void oddEvenSortEmptyArray(){
+        int[] inputArray = {};
+        oddEvenSort.oddEvenSort(inputArray);
+        int[] expectedOutput = {};
+        assertArrayEquals(inputArray, expectedOutput);
+    }
+
+    @Test
+    public void oddEvenSortNaturalNumberArray(){
+        int[] inputArray = {18, 91, 86, 60, 21, 44, 37, 78, 98, 67};
+        oddEvenSort.oddEvenSort(inputArray);
+        int[] expectedOutput = {18, 21, 37, 44, 60, 67, 78, 86, 91, 98};
+        assertArrayEquals(inputArray, expectedOutput);
+    }
+
+    @Test
+    public void oddEvenSortIntegerArray(){
+        int[] inputArray = {57, 69, -45, 12, -85, 3, -76, 36, 67, -14};
+        oddEvenSort.oddEvenSort(inputArray);
+        int[] expectedOutput = {-85, -76, -45, -14, 3, 12, 36, 57, 67, 69};
+        assertArrayEquals(inputArray, expectedOutput);
+    }
+    
+}