Test linked list in both directions in base tile hash.

common/basetilehash_test.go

@@ -26,7 +26,27 @@ func randomBaseTileHash(updates int) *BaseTileHash {
 	return bth
 }
 
-func TestBaseTileHash(t *testing.T) {
+func TestBaseTileHashLenList(t *testing.T) {
+	for _, updates := range []int{53, 111, 1345, 11261} {
+		bth := randomBaseTileHash(updates)
+		countNext := 0
+		for cur := bth.root.next; cur != &bth.root; cur = cur.next {
+			countNext++
+		}
+		countPrev := 0
+		for cur := bth.root.prev; cur != &bth.root; cur = cur.prev {
+			countPrev++
+		}
+		if countPrev != countNext {
+			t.Errorf("count prev != count next: %d %d", countPrev, countNext)
+		}
+		if countPrev != len(bth.hashes) {
+			t.Errorf("count prev != len(hash): %d %d", countPrev, len(bth.hashes))
+		}
+	}
+}
+
+func TestBaseTileHashIntegrity(t *testing.T) {
 	for _, updates := range []int{10, 100, 1000, 10000} {
 		bth := randomBaseTileHash(updates)
 		entries := map[*btHashEntry]bool{}