Add LineScanner and SpanScanner classes to string_scanner.

pkg/string_scanner/test/string_scanner_test.dart

 // Copyright (c) 2014, 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 string_scanner.string_scanner_test;
 
 import 'package:string_scanner/string_scanner.dart';
 import 'package:unittest/unittest.dart';
 
 void main() {
@@ skipping 13 matching lines @@
     });
 
     test('lastMatch is null', () {
       expect(scanner.lastMatch, isNull);
     });
 
     test('position is zero', () {
       expect(scanner.position, equals(0));
     });
 
+    test("readChar fails and doesn't change the state", () {
+      expect(scanner.readChar, throwsFormatException);
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+    });
+
+    test("peekChar returns null and doesn't change the state", () {
+      expect(scanner.peekChar(), isNull);
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+    });
+
     test("scan returns false and doesn't change the state", () {
       expect(scanner.scan(new RegExp('.')), isFalse);
       expect(scanner.lastMatch, isNull);
       expect(scanner.position, equals(0));
     });
 
     test("expect throws a FormatException and doesn't change the state", () {
       expect(() => scanner.expect(new RegExp('.')), throwsFormatException);
       expect(scanner.lastMatch, isNull);
       expect(scanner.position, equals(0));
@@ skipping 34 matching lines @@
     });
 
     test('lastMatch is null', () {
       expect(scanner.lastMatch, isNull);
     });
 
     test('position is zero', () {
       expect(scanner.position, equals(0));
     });
 
+    test('readChar returns the first character and moves forward', () {
+      expect(scanner.readChar(), equals(0x66));
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(1));
+    });
+
+    test('peekChar returns the first character', () {
+      expect(scanner.peekChar(), equals(0x66));
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+    });
+
+    test('peekChar with an argument returns the nth character', () {
+      expect(scanner.peekChar(4), equals(0x62));
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+    });
+
     test("a matching scan returns true and changes the state", () {
       expect(scanner.scan(new RegExp('f(..)')), isTrue);
       expect(scanner.lastMatch[1], equals('oo'));
       expect(scanner.position, equals(3));
       expect(scanner.rest, equals(' bar'));
     });
 
     test("a non-matching scan returns false and sets lastMatch to null", () {
       expect(scanner.matches(new RegExp('f(..)')), isTrue);
       expect(scanner.lastMatch, isNotNull);
@@ skipping 95 matching lines @@
     });
 
     test('rest is empty', () {
       expect(scanner.rest, isEmpty);
     });
 
     test('position is zero', () {
       expect(scanner.position, equals(7));
     });
 
+    test("readChar fails and doesn't change the state", () {
+      expect(scanner.readChar, throwsFormatException);
+      expect(scanner.lastMatch, isNotNull);
+      expect(scanner.position, equals(7));
+    });
+
+    test("peekChar returns null and doesn't change the state", () {
+      expect(scanner.peekChar(), isNull);
+      expect(scanner.lastMatch, isNotNull);
+      expect(scanner.position, equals(7));
+    });
+
     test("scan returns false and sets lastMatch to null", () {
       expect(scanner.scan(new RegExp('.')), isFalse);
       expect(scanner.lastMatch, isNull);
       expect(scanner.position, equals(7));
     });
 
     test("expect throws a FormatException and sets lastMatch to null", () {
       expect(() => scanner.expect(new RegExp('.')), throwsFormatException);
       expect(scanner.lastMatch, isNull);
       expect(scanner.position, equals(7));
@@ skipping 45 matching lines @@
       expect(() => new StringScanner('foo bar', position: -1),
           throwsArgumentError);
     });
 
     test('throws an ArgumentError if the position is beyond the string', () {
       expect(() => new StringScanner('foo bar', position: 8),
           throwsArgumentError);
     });
   });
 }