Don't use private testtools.test module

The testtools.test module is the unit testing module for testtools and
is an internal module with additional requirements. We should not be
relying on this module.

Copy the tests that were exposed from testtools into here.

Change-Id: I1e09228cff7a0c8136447f07df6864045a6fb849

keystoneauth1/tests/unit/test_matchers.py

@@ -13,12 +13,15 @@
 # under the License.
 
 import testtools
-from testtools.tests.matchers import helpers
+from testtools import matchers as tt_matchers
 
-from keystoneauth1.tests.unit import matchers
+from keystoneauth1.tests.unit import matchers as ks_matchers
+
+# NOTE(jamielennox): The tests in this file are copied form the non-public
+# testtools.tests.matchers.helpers.TestMatchersInterface.
 
 
-class TestXMLEquals(testtools.TestCase, helpers.TestMatchersInterface):
+class TestXMLEquals(testtools.TestCase):
     matches_xml = b"""<?xml version="1.0" encoding="UTF-8"?>
 <test xmlns="http://docs.openstack.org/identity/api/v2.0">
     <first z="0" y="1" x="2"/>
@@ -48,10 +51,43 @@ actual =
 </test>
 """
 
-    matches_matcher = matchers.XMLEquals(matches_xml)
+    matches_matcher = ks_matchers.XMLEquals(matches_xml)
     matches_matches = [matches_xml, equivalent_xml]
     matches_mismatches = [mismatches_xml]
     describe_examples = [
         (mismatches_description, mismatches_xml, matches_matcher),
     ]
     str_examples = [('XMLEquals(%r)' % matches_xml, matches_matcher)]
+
+    def test_matches_match(self):
+        matcher = self.matches_matcher
+        matches = self.matches_matches
+        mismatches = self.matches_mismatches
+        for candidate in matches:
+            self.assertEqual(None, matcher.match(candidate))
+        for candidate in mismatches:
+            mismatch = matcher.match(candidate)
+            self.assertNotEqual(None, mismatch)
+            self.assertNotEqual(None, getattr(mismatch, 'describe', None))
+
+    def test__str__(self):
+        # [(expected, object to __str__)].
+        examples = self.str_examples
+        for expected, matcher in examples:
+            self.assertThat(matcher, tt_matchers.DocTestMatches(expected))
+
+    def test_describe_difference(self):
+        # [(expected, matchee, matcher), ...]
+        examples = self.describe_examples
+        for difference, matchee, matcher in examples:
+            mismatch = matcher.match(matchee)
+            self.assertEqual(difference, mismatch.describe())
+
+    def test_mismatch_details(self):
+        # The mismatch object must provide get_details, which must return a
+        # dictionary mapping names to Content objects.
+        examples = self.describe_examples
+        for difference, matchee, matcher in examples:
+            mismatch = matcher.match(matchee)
+            details = mismatch.get_details()
+            self.assertEqual(dict(details), details)