fixed double linked list and create test for it

Author: Miraddo

datastructures/linkedlist/doublylinkedlist/doublylinkedlist.go

@@ -28,7 +28,13 @@ func NewNode(val int) *Node {
 func (ll *DoubleLinkedList) AddAtBeg(val int) {
 	n := NewNode(val)
 	n.next = ll.head
+
+	if ll.head != nil{
+		ll.head.prev = n
+	}
+
 	ll.head = n
+
 }
 
 // AddAtEnd Add a node at the end of the linkedlist

datastructures/linkedlist/doublylinkedlist/doublylinkedlist_test.go

@@ -0,0 +1,88 @@
+package doublylinkedlist
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestDoubleLinkedList(t *testing.T) {
+	newList := DoubleLinkedList{}
+
+	newList.AddAtBeg(1)
+	newList.AddAtBeg(2)
+	newList.AddAtBeg(3)
+
+	t.Run("Test AddAtBeg", func(t *testing.T) {
+		wantNext := []int{3, 2, 1}
+		wantPrev := []int{1, 2, 3}
+		got := []int{}
+
+		// check from next address
+		current := newList.head
+
+		got = append(got, current.val)
+
+		for current.next != nil {
+			current = current.next
+			got = append(got, current.val)
+		}
+
+		if !reflect.DeepEqual(got, wantNext) {
+			t.Errorf("got: %v, want: %v", got, wantNext)
+		}
+
+		// check from prev address
+		got = []int{}
+		got = append(got, current.val)
+
+		for current.prev != nil {
+			current = current.prev
+			got = append(got, current.val)
+		}
+
+		if !reflect.DeepEqual(got, wantPrev) {
+			t.Errorf("got: %v, want: %v", got, wantPrev)
+		}
+	})
+
+	newList.AddAtEnd(4)
+
+	t.Run("Test AddAtEnd", func(t *testing.T) {
+		want := []int{3, 2, 1, 4}
+		got := []int{}
+		current := newList.head
+		got = append(got, current.val)
+		for current.next != nil {
+			current = current.next
+			got = append(got, current.val)
+		}
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("got: %v, want: %v", got, want)
+		}
+	})
+
+	t.Run("Test DelAtBeg", func(t *testing.T) {
+		want := 3
+		got := newList.DelAtBeg()
+		if got != want {
+			t.Errorf("got: %v, want: %v", got, want)
+		}
+	})
+
+	t.Run("Test DelAtEnd", func(t *testing.T) {
+		want := 4
+		got := newList.DelAtEnd()
+		if got != want {
+			t.Errorf("got: %v, want: %v", got, want)
+		}
+	})
+
+	t.Run("Test Count", func(t *testing.T) {
+		want := 2
+		got := newList.Count()
+		if got != want {
+			t.Errorf("got: %v, want: %v", got, want)
+		}
+	})
+
+}