Strings recipes for the Dart Cookbook

recipes/test/core/strings/concatenating_strings_test.dart

+library concatenating_strings_test;
+
+import 'package:unittest/unittest.dart';
+
+String filmToWatch() => 'The Big Lebowski';
+
+void main() { 
+  group('concatenating strings', () {
+    group('using adjacent string literals', () {
+      test('on one line', () {
+        expect('Dart' ' is' ' fun!', equals('Dart is fun!'));
+      });
+      
+      test('over many lines', () {
+        expect('Dart' 
+            ' is' 
+            ' fun!', equals('Dart is fun!'));
+      });
+      
+      test('over one or many lines', () {
+        expect('Dart' ' is' 
+            ' fun!', equals('Dart is fun!'));
+      });
+      
+      test('using multiline strings', () {
+        expect('''Peanut
+butter '''
+'''and
+jelly''', equals('Peanut\nbutter and\njelly'));
+      });
+        
+      test('combining single and multiline string', () {
+        expect('Dewey ' 'Cheatem'
+            ''' and
+Howe''', equals('Dewey Cheatem and\nHowe'));
+      });
+    });
+  
+    group('using alternatives to string literals', () {
+      test(': concat()', () {
+        var film = filmToWatch();
+        film = film.concat('\n');
+        expect(film, equals('The Big Lebowski\n')); 
+      });
+    
+      test(': join()', () {
+        expect(['The', 'Big', 'Lebowski'].join(' '), equals('The Big Lebowski'));
+      });
+    });
+  });
+}