Update PriorityQueueSortTest.java

Author: Rahul-150705

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

@@ -5,6 +5,19 @@
 
 class PriorityQueueSortTest {
 
+    @Test
+    void testNullArray() {
+        int[] input = null;
+        assertArrayEquals(null, PriorityQueueSort.sort(input));
+    }
+
+    @Test
+    void testSingleElementArray() {
+        int[] input = {5};
+        int[] expected = {5};
+        assertArrayEquals(expected, PriorityQueueSort.sort(input));
+    }
+
     @Test
     void testSortNormalArray() {
         int[] input = {7, 2, 9, 4, 1};