More tests

.gitignore

@@ -23,3 +23,5 @@ go.work.sum
 
 # env file
 .env
+
+cov.html

list/list.go

@@ -105,8 +105,8 @@ func (lst *List[T]) Remove(node *Node[T]) {
 	lst.length--
 }
 
-// All returns an iterator over all the values in the list.
-func (lst *List[T]) All() iter.Seq[T] {
+// Values returns an iterator over all the values in the list.
+func (lst *List[T]) Values() iter.Seq[T] {
 	return func(yield func(T) bool) {
 		for node := lst.front.next; node != lst.back; node = node.next {
 			if !yield(node.Value) {
@@ -116,6 +116,17 @@ func (lst *List[T]) All() iter.Seq[T] {
 	}
 }
 
+// Nodes returns an iterator over all the nodes in the list.
+func (lst *List[T]) Nodes() iter.Seq[*Node[T]] {
+	return func(yield func(*Node[T]) bool) {
+		for node := lst.front.next; node != lst.back; node = node.next {
+			if !yield(node) {
+				return
+			}
+		}
+	}
+}
+
 func (lst *List[T]) debugPrint() {
 	fmt.Println("-----------------------")
 	for n := lst.front; n != nil; n = n.next {

list/list_test.go

@@ -11,10 +11,39 @@ func checkList[T comparable](t *testing.T, lst *List[T], want []T) {
 		t.Errorf("got len=%v, want %v", lst.Len(), len(want))
 	}
 
-	got := slices.Collect(lst.All())
+	got := slices.Collect(lst.Values())
 	if !slices.Equal(got, want) {
 		t.Errorf("got %v, want %v", got, want)
 	}
+
+	if lst.front.prev != nil {
+		t.Errorf("got lst.front.prev=%p, want nil", lst.front.prev)
+	}
+	if lst.back.next != nil {
+		t.Errorf("got lst.back.next=%p, want nil", lst.back.next)
+	}
+
+	if lst.Len() < 1 {
+		return
+	}
+	// Get all nodes from the list and verify list invariants.
+	nodes := slices.Collect(lst.Nodes())
+	first := nodes[0]
+	last := nodes[len(nodes)-1]
+
+	if lst.front.next != first || first.prev != lst.front {
+		t.Errorf("front mismatch: front.next=%p, first.prev=%p", lst.front.next, first.prev)
+	}
+	if lst.back.prev != last || last.next != lst.back {
+		t.Errorf("back mismatch: back.prev=%p, last.next=%p", lst.back.prev, last.next)
+	}
+
+	for i := 0; i < len(nodes)-1; i++ {
+		j := i + 1
+		if nodes[i].next != nodes[j] || nodes[j].prev != nodes[i] {
+			t.Errorf("node link mismatch at i=%d, j=%d", i, j)
+		}
+	}
 }
 
 func TestBasicInsertFront(t *testing.T) {
@@ -93,3 +122,46 @@ func TestRemove(t *testing.T) {
 	nl.Remove(nl.Back())
 	checkList(t, nl, []int{})
 }
+
+func TestFrontBack(t *testing.T) {
+	// Empty list - nil for both
+	nl := New[int]()
+	if nl.Front() != nil {
+		t.Errorf("got front=%v, want nil", nl.Front())
+	}
+	if nl.Back() != nil {
+		t.Errorf("got back=%v, want nil", nl.Back())
+	}
+
+	// Insert element
+	nl.InsertBack(50)
+	if nl.Front().Value != 50 || nl.Back().Value != 50 {
+		t.Errorf("got front=%v, back=%v, want 50", nl.Front().Value, nl.Back().Value)
+	}
+}
+
+func TestNextPrev(t *testing.T) {
+	nl := New[string]()
+	nl.InsertBack("five")
+	nl.InsertBack("six")
+	nl.InsertBack("seven")
+
+	var vals []string
+	for n := nl.Front(); n != nil; n = nl.Next(n) {
+		vals = append(vals, n.Value)
+	}
+
+	wantVals := []string{"five", "six", "seven"}
+	if !slices.Equal(vals, wantVals) {
+		t.Errorf("got %v, want %v", vals, wantVals)
+	}
+
+	var revVals []string
+	for n := nl.Back(); n != nil; n = nl.Prev(n) {
+		revVals = append(revVals, n.Value)
+	}
+	slices.Reverse(revVals)
+	if !slices.Equal(revVals, wantVals) {
+		t.Errorf("got %v, want %v", revVals, wantVals)
+	}
+}