public void Merge_head1Null_Rethead2()
        {
            // Arrange
            // head1 = null
            // head2 = null
            Node head1 = null;
            Node node3 = new Node();

            node3.data = 3;
            node3.next = null;

            Node node2 = new Node();

            node2.data = 2;
            node2.next = node3;

            Node node1 = new Node();

            node1.data = 1;
            node1.next = node2;

            Node head2 = node1;

            var  sortProcessor = new MergeSortedLinkedLists();
            Node actualNode    = sortProcessor.Merge(head1, head2);
            var  actual        = sortProcessor.printData(actualNode);
            var  expected      = "1,2,3";

            // Act
            actualNode = sortProcessor.Merge(head1, head2);

            // Assert
            Assert.AreEqual(expected, actual);
        }
        public void Merge_head1_134_head2_25_return_12345()
        {
            // Arrange
            // head1 = 1,3,4
            // head2 = 2,5
            Node head1 = new Node();

            head1.data           = 1;
            head1.next           = new Node();
            head1.next.data      = 3;
            head1.next.next      = new Node();
            head1.next.next.data = 4;
            head1.next.next.next = null;

            Node head2 = new Node();

            head2.data      = 2;
            head2.next      = new Node();
            head2.next.data = 5;
            head2.next.next = null;

            var sortProcessor = new MergeSortedLinkedLists();
            var actualNode    = new Node();
            var actual        = String.Empty;
            var expected      = "1,2,3,4,5";

            // Act
            actualNode = sortProcessor.Merge(head1, head2);
            actual     = sortProcessor.printData(actualNode);
            // Assert
            Assert.AreEqual(expected, actual);
        }
        public void Merge_2NullArray_RetNull()
        {
            // Arrange
            // head1 = null
            // head2 = null
            Node head1 = null;
            Node head2 = null;

            var  sortProcessor = new MergeSortedLinkedLists();
            Node actualNode    = null;

            // Act
            actualNode = sortProcessor.Merge(head1, head2);

            // Assert
            Assert.Null(actualNode);
        }