Strings recipes for the Dart Cookbook

recipes/test/core/strings/subscripting_a_string_test.dart

+library subscripting_a_string_test;
+
+import 'package:unittest/unittest.dart';
+
+void main() {
+  group('getting the character at a specific index', () {
+    group("with non-BMP symbol", () {
+      test('with non-BMP symbol', () {
+        var coffee = '\u{1F375}';
+        expect(coffee.runes.toList(), equals([127861]));
+        expect(new String.fromCharCode(coffee.runes.first),
+          equals(coffee));
+        // Cannot use coffee[0] directly.
+        expect(coffee.codeUnits.first, equals(55356));
+        expect(coffee.codeUnits.toList()[0], equals(55356));
+      }); 
+    });
+
+    group('with BMP symbol', () {
+      
+      test('with BMP symbols', () {
+        expect('Dart'[0], equals('D'));
+
+        var hearts = '\u2661';
+        expect(hearts[0], equals('\u2661'));
+      });      
+    });
+  });
+}