Just another update

Task/Reverse-a-string/Dart/reverse-a-string-1.dart

@@ -0,0 +1 @@
+String reverse(String s) => new String.fromCharCodes(s.runes.toList().reversed);

Task/Reverse-a-string/Dart/reverse-a-string-2.dart

@@ -0,0 +1,17 @@
+import 'package:unittest/unittest.dart';
+
+String reverse(String s) => new String.fromCharCodes(s.runes.toList().reversed);
+
+main() {
+  group("Reverse a string -", () {
+    test("Strings with ASCII characters are reversed correctly.", () {
+      expect(reverse("hello, world"), equals("dlrow ,olleh"));
+    });
+    test("Strings with non-ASCII BMP characters are reversed correctly.", () {
+      expect(reverse("\u4F60\u4EEC\u597D"), equals("\u597D\u4EEC\u4F60"));
+    });
+    test("Strings with non-BMP characters are reversed correctly.", () {
+      expect(reverse("hello, \u{1F310}"), equals("\u{1F310} ,olleh"));
+    });
+  });
+}

Task/Reverse-a-string/Dart/reverse-a-string.dart

@@ -1,11 +0,0 @@
-String reverse(String s) {
-  StringBuffer sb=new StringBuffer();
-  for(int i=s.length-1;i>=0;i--) {
-    sb.add(s[i]);
-  }
-  return sb.toString();
-}
-
-main() {
-  print(reverse('a string.'));
-}