Add isNotEmpty to core_matchers.

pkg/matcher/test/string_matchers_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library matcher.string_matchers_test;
 
 import 'package:matcher/matcher.dart';
 import 'package:unittest/unittest.dart' show test, group;
 
 import 'test_utils.dart';
 
 void main() {
   initUtils();
 
   test('collapseWhitespace', () {
     var source = '\t\r\n hello\t\r\n world\r\t \n';
     expect(collapseWhitespace(source), 'hello world');
   });
 
   test('isEmpty', () {
     shouldPass('', isEmpty);
     shouldFail(null, isEmpty, "Expected: empty Actual: <null>");
     shouldFail(0, isEmpty, "Expected: empty Actual: <0>");
     shouldFail('a', isEmpty, "Expected: empty Actual: 'a'");
   });
 
+  test('isNotEmpty', () {
+    shouldFail('', isNotEmpty, "Expected: non-empty Actual: ''");
+    shouldFail(null, isNotEmpty, "Expected: non-empty Actual: <null>");
+    shouldFail(0, isNotEmpty, "Expected: non-empty Actual: <0>");
+    shouldPass('a', isNotEmpty);
+  });
+
   test('equalsIgnoringCase', () {
     shouldPass('hello', equalsIgnoringCase('HELLO'));
     shouldFail('hi', equalsIgnoringCase('HELLO'),
         "Expected: 'HELLO' ignoring case Actual: 'hi'");
   });
 
   test('equalsIgnoringWhitespace', () {
     shouldPass(' hello   world  ', equalsIgnoringWhitespace('hello world'));
     shouldFail(' helloworld  ', equalsIgnoringWhitespace('hello world'),
         "Expected: 'hello world' ignoring whitespace "
@@ skipping 48 matching lines @@
       "Actual: 'goodbye cruel world'");
   });
 
   test('matches', () {
     shouldPass('c0d', matches('[a-z][0-9][a-z]'));
     shouldPass('c0d', matches(new RegExp('[a-z][0-9][a-z]')));
     shouldFail('cOd', matches('[a-z][0-9][a-z]'),
         "Expected: match '[a-z][0-9][a-z]' Actual: 'cOd'");
   });
 }