Correctly match and print strings with escaped values

test/escape_test.dart

+// Copyright (c) 2015, 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.escape_test;
+
+import 'package:matcher/src/util.dart';
+import 'package:unittest/unittest.dart';
+
+void main() {
+  group('escaping should work with', () {
+    _testEscaping('no escaped chars', 'Hello, world!', 'Hello, world!');
+    _testEscaping('newline', '\n', r'\n');
+    _testEscaping('carriage return', '\r', r'\r');
+    _testEscaping('form feed', '\f', r'\f');
+    _testEscaping('backspace', '\b', r'\b');
+    _testEscaping('tab', '\t', r'\t');
+    _testEscaping('vertical tab', '\v', r'\v');
+    _testEscaping('escape combos', r'\n', r'\\n');
+    _testEscaping('All characters',
+        'A new line\nA charriage return\rA form feed\fA backspace\b'
+        'A tab\tA vertical tab\vA slash\\',
+        r'A new line\nA charriage return\rA form feed\fA backspace\b'
+        r'A tab\tA vertical tab\vA slash\\');
+  });
+
+  group('unequal strings remain unequal when escaped', () {
+    _testUnequalStrings('with a newline', '\n', r'\n');
+    _testUnequalStrings('with slash literals', '\\', r'\\');
+  });
+}
+
+/// Creates a [test] with name [name] that verifies [source] escapes to value
+/// [target].
+void _testEscaping(String name, String source, String target) {
+  test(name, () {
+    var escaped = escape(source);
+    expect(escaped == target, isTrue,
+        reason: "Expected escaped value: $target\n"
+        "  Actual escaped value: $escaped");
+  });
+}
+
+/// Creates a [test] with name [name] that ensures two different [String] values
+/// [s1] and [s2] remain unequal when escaped.
+void _testUnequalStrings(String name, String s1, String s2) {
+  test(name, () {
+    // Explicitly not using the equals matcher
+    expect(s1 != s2, isTrue, reason: 'The source values should be unequal');
+
+    var escapedS1 = escape(s1);
+    var escapedS2 = escape(s2);
+
+    // Explicitly not using the equals matcher
+    expect(escapedS1 != escapedS2, isTrue,
+        reason: 'Unequal strings, when escaped, should remain unequal.');
+  });
+}