questions.yn: Perform string, not identity, comparison against 'y'

The `is` operator performs object identity comparison.  Changing to `==`
implements the expected behavior.

Use the mock library to add tests verifying the API of questions.yn.

setup.py

@@ -123,6 +123,10 @@ setup(
         'python-dateutil <2.0,>=1.3',
         'feedparser',
         ],
+
+    tests_require=[
+        'mock',
+    ]
     )
 
 

src/questions.py

@@ -112,7 +112,7 @@ def yn(prompt, default=None):
         else:
             default = 'n'
     s = expect(prompt, ['y', 'n'], default=default)
-    if s is 'y':
+    if s == 'y':
         return True
     else:
         return False

test/test_yn.py

@@ -0,0 +1,99 @@
+###
+# Copyright (c) 2014, Artur Krysiak
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+#   * Redistributions of source code must retain the above copyright notice,
+#     this list of conditions, and the following disclaimer.
+#   * Redistributions in binary form must reproduce the above copyright notice,
+#     this list of conditions, and the following disclaimer in the
+#     documentation and/or other materials provided with the distribution.
+#   * Neither the name of the author of this software nor the name of
+#     contributors to this software may be used to endorse or promote products
+#     derived from this software without specific prior written consent.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+###
+
+from supybot import questions
+from supybot.test import SupyTestCase
+
+import mock
+
+# so complicated construction because I want to
+# gain the string 'y' instead of the character 'y'
+# the reason of usage this construction is to prove
+# that comparing strings by 'is' is wrong
+# better solution is usage of '==' operator ;)
+_yes_answer = ''.join(['', 'y'])
+
+class TestYn(SupyTestCase):
+    def test_default_yes_selected(self):
+        questions.expect = mock.Mock(return_value=_yes_answer)
+
+        answer = questions.yn('up', default='y')
+
+        self.assertTrue(answer)
+
+    def test_default_no_selected(self):
+        questions.expect = mock.Mock(return_value='n')
+
+        answer = questions.yn('up', default='n')
+
+        self.assertFalse(answer)
+
+    def test_yes_selected_without_defaults(self):
+        questions.expect = mock.Mock(return_value=_yes_answer)
+
+        answer = questions.yn('up')
+
+        self.assertTrue(answer)
+
+    def test_no_selected_without_defaults(self):
+        questions.expect = mock.Mock(return_value='n')
+
+        answer = questions.yn('up')
+
+        self.assertFalse(answer)
+
+    def test_no_selected_with_default_yes(self):
+        questions.expect = mock.Mock(return_value='n')
+
+        answer = questions.yn('up', default='y')
+
+        self.assertFalse(answer)
+
+    def test_yes_selected_with_default_yes(self):
+        questions.expect = mock.Mock(return_value=_yes_answer)
+
+        answer = questions.yn('up', default='y')
+
+        self.assertTrue(answer)
+
+    def test_yes_selected_with_default_no(self):
+        questions.expect = mock.Mock(return_value=_yes_answer)
+
+        answer = questions.yn('up', default='n')
+
+        self.assertTrue(answer)
+
+    def test_no_selected_with_default_no(self):
+        questions.expect = mock.Mock(return_value='n')
+
+        answer = questions.yn('up', default='n')
+
+        self.assertFalse(answer)
+
+# vim:set shiftwidth=4 softtabstop=4 expandtab textwidth=79: