feat: junit test for radixsort

Author: yeoshuheng

src/test/java/algorithms/sorting/radixSort/RadixSortTest.java

@@ -0,0 +1,39 @@
+package algorithms.sorting.radixSort;
+
+import static org.junit.Assert.assertArrayEquals;
+import org.junit.Test;
+import java.util.Arrays;
+public class RadixSortTest {
+  @Test
+  public void test_radixSort_shouldReturnSortedArray() {
+    int[] firstArray =
+      new int[] {2, 3, 4, 1, 2, 5, 6, 7, 10, 15, 20, 13, 15, 1, 2,
+        15, 12, 20, 21, 120, 11, 5, 7, 85, 30};
+    int[] firstResult = Arrays.copyOf(firstArray, firstArray.length);
+    RadixSort.radixSort(firstResult);
+
+    int[] secondArray
+      = new int[] {9, 1, 2, 8, 7, 3, 4, 6, 5, 5, 9, 8, 7, 6, 5, 4,
+      3, 2, 1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+    int[] secondResult =Arrays.copyOf(secondArray, secondArray.length);
+    RadixSort.radixSort(secondResult);
+
+    int[] thirdArray = new int[] {};
+    int[] thirdResult = Arrays.copyOf(thirdArray, thirdArray.length);
+    RadixSort.radixSort(thirdResult);
+
+    int[] fourthArray = new int[] {1};
+    int[] fourthResult = Arrays.copyOf(fourthArray, fourthArray.length);
+    RadixSort.radixSort(fourthResult);
+
+    Arrays.sort(firstArray);
+    Arrays.sort(secondArray);
+    Arrays.sort(thirdArray);
+    Arrays.sort(fourthArray);
+
+    assertArrayEquals(firstResult, firstArray);
+    assertArrayEquals(secondResult, secondArray);
+    assertArrayEquals(thirdResult, thirdArray);
+    assertArrayEquals(fourthResult, fourthArray);
+  }
+}