Strings recipes for the Dart Cookbook

recipes/test/core/strings/calculating_the_length_test.dart

+library calculating_the_length_test;
+
+import 'package:unittest/unittest.dart';
+
+void main() {
+  group('calculating the length of a string', () {
+    
+    var hearts = '\u2661';
+
+    test('that contains only BMP symbols', () {
+      expect('I love music'.length, equals(12));
+      expect('I love music'.runes.length, equals(12));
+
+      expect(hearts.length, equals(1));
+      expect(hearts.runes.length, equals(1));
+    });
+    
+    test('that contains non-BMP symbols', () {
+      var clef = '\u{1F3BC}';
+      expect(clef.length, equals(2));
+      expect(clef.runes.length, equals(1));
+
+      var music = 'I $hearts $clef';
+      expect(music.length, equals(6));
+      expect(music.runes.length, equals(5));
+    });
+  });
+}