Create BucketSortTest (TheAlgorithms#3779)

* Create BucketSortTest

* Update src/test/java/com/thealgorithms/sorts/BucketSortTest.java

Co-authored-by: Debasish Biswas <debasishbsws.abc@gmail.com>

Co-authored-by: Debasish Biswas <debasishbsws.abc@gmail.com>

Author: hyeonmin2

src/main/java/com/thealgorithms/sorts/BucketSort.java

@@ -32,7 +32,7 @@ public static void main(String[] args) {
      *
      * @param arr the array contains elements
      */
-    private static void bucketSort(int[] arr) {
+    public static int[] bucketSort(int[] arr) {
         /* get max value of arr */
         int max = max(arr);
 
@@ -67,6 +67,8 @@ private static void bucketSort(int[] arr) {
                 arr[index++] = value;
             }
         }
+        
+        return arr;
     }
 
     /**

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

@@ -0,0 +1,48 @@
+package com.thealgorithms.sorts;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class BucketSortTest {
+
+    @Test
+    public void bucketSortSingleIntegerArray() {
+        int[] inputArray = { 4 };
+        int[] outputArray = BucketSort.bucketSort(inputArray);
+        int[] expectedOutput = { 4 };
+        assertArrayEquals(outputArray, expectedOutput);
+    }
+
+    @Test
+    public void bucketSortNonDuplicateIntegerArray() {
+        int[] inputArray = { 6, 1, 99, 27, 15, 23, 36 };
+        int[] outputArray = BucketSort.bucketSort(inputArray);
+        int[] expectedOutput = {1, 6, 15, 23, 27, 36, 99};
+        assertArrayEquals(outputArray, expectedOutput);
+    }
+
+    @Test
+    public void bucketSortDuplicateIntegerArray() {
+        int[] inputArray = { 6, 1, 27, 15, 23, 27, 36, 23 };
+        int[] outputArray = BucketSort.bucketSort(inputArray);
+        int[] expectedOutput = {1, 6, 15, 23, 23, 27, 27, 36};
+        assertArrayEquals(outputArray, expectedOutput);
+    }
+
+    @Test
+    public void bucketSortNonDuplicateIntegerArrayWithNegativeNum() {
+        int[] inputArray = {  6, -1, 99, 27, -15, 23, -36  };
+        int[] outputArray = BucketSort.bucketSort(inputArray);
+        int[] expectedOutput = { -36, -15, -1, 6, 23, 27, 99};
+        assertArrayEquals(outputArray, expectedOutput);
+    }
+
+    @Test
+    public void bucketSortDuplicateIntegerArrayWithNegativeNum() {
+        int[] inputArray = { 6, -1, 27, -15, 23, 27, -36, 23  };
+        int[] outputArray = BucketSort.bucketSort(inputArray);
+        int[] expectedOutput = { -36, -15, -1, 6, 23, 23, 27, 27};
+        assertArrayEquals(outputArray, expectedOutput);
+    }
+}