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[Jonathan Lange <jml@xxxxxxxxxxxxx>]

Jonathan Lange has proposed merging lp:~jml/testtools/basic-mismatch into lp:testtools.

Requested reviews:
  testtools developers (testtools-dev)


This branch changes the base "Mismatch" so that it takes optional description and details parameters.

I wanted to do this because for a lot of Matchers I don't really want to make my own Mismatch subclass and I shouldn't need to.

As for implementation, I've preserved the old API, but am not particularly happy with the gymnastics required to do so. I could have my arm twisted to move the changes out of the base class and into a new class like SimpleMismatch. The reason I didn't is that I think Mismatch("description") is a less surprising API for users than a second class.

Māris points out that with this change, many of the Mismatch classes in testtools.matchers could disappear, along with their nice names.


-- 
https://code.launchpad.net/~jml/testtools/basic-mismatch/+merge/32872
Your team testtools developers is requested to review the proposed merge of lp:~jml/testtools/basic-mismatch into lp:testtools.

=== modified file 'NEWS'
--- NEWS	2010-08-05 10:19:28 +0000
+++ NEWS	2010-08-17 13:15:56 +0000
@@ -7,6 +7,9 @@
 Improvements
 ------------
 
+ * 'Mismatch' now takes optional description and details parameters, so
+   custom Matchers aren't compelled to make their own subclass.
+
  * jml added a built-in UTF8_TEXT ContentType to make it slightly easier to
    add details to test results.
 
@@ -16,7 +19,7 @@
  * New 'Is' matcher, which lets you assert that a thing is identical to
    another thing.
 
- * New 'LessThan' matcher which lets you assert that a thing is less than 
+ * New 'LessThan' matcher which lets you assert that a thing is less than
    another thing.
 
  * TestCase now has a 'patch()' method to make it easier to monkey-patching

=== modified file 'testtools/matchers.py'
--- testtools/matchers.py	2010-08-05 06:20:48 +0000
+++ testtools/matchers.py	2010-08-17 13:15:56 +0000
@@ -58,12 +58,29 @@
 class Mismatch(object):
     """An object describing a mismatch detected by a Matcher."""
 
+    def __init__(self, description=None, details=None):
+        """Construct a `Mismatch`.
+
+        :param description: A description to use.  If not provided,
+            `Mismatch.describe` must be implemented.
+        :param details: Extra details about the mismatch.  Defaults
+            to the empty dict.
+        """
+        if description:
+            self._description = description
+        if details is None:
+            details = {}
+        self._details = details
+
     def describe(self):
         """Describe the mismatch.
 
         This should be either a human-readable string or castable to a string.
         """
-        raise NotImplementedError(self.describe_difference)
+        try:
+            return self._description
+        except AttributeError:
+            raise NotImplementedError(self.describe)
 
     def get_details(self):
         """Get extra details about the mismatch.
@@ -81,7 +98,7 @@
             to the result. For more information see the API to which items from
             this dict are passed testtools.TestCase.addDetail.
         """
-        return {}
+        return getattr(self, '_details', {})
 
 
 class DocTestMatches(object):

=== modified file 'testtools/tests/test_matchers.py'
--- testtools/tests/test_matchers.py	2010-08-05 06:20:48 +0000
+++ testtools/tests/test_matchers.py	2010-08-17 13:15:56 +0000
@@ -16,6 +16,7 @@
     LessThan,
     MatchesAny,
     MatchesAll,
+    Mismatch,
     Not,
     NotEquals,
     )
@@ -24,6 +25,19 @@
 Matcher
 
 
+class TestMismatch(TestCase):
+
+    def test_constructor_arguments(self):
+        mismatch = Mismatch("some description", {'detail': "things"})
+        self.assertEqual("some description", mismatch.describe())
+        self.assertEqual({'detail': "things"}, mismatch.get_details())
+
+    def test_constructor_no_arguments(self):
+        mismatch = Mismatch()
+        self.assertRaises(NotImplementedError, mismatch.describe)
+        self.assertEqual({}, mismatch.get_details())
+
+
 class TestMatchersInterface(object):
 
     def test_matches_match(self):