Strings recipes for the Dart Cookbook

recipes/test/core/strings/concatenating_strings_test.dart

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