Embellish fixture assertions with the path.

Author: albu-diku

tests/support/__init__.py

@@ -46,6 +46,21 @@
 
 from tests.support._env import MIG_ENV, PY2
 
+# Alow the use of SimpleNamespace on PY2.
+
+if PY2:
+    class SimpleNamespace(dict):
+        """Bare minimum SimpleNamespace for Python 2."""
+
+        def __getattribute__(self, name):
+            if name == '__dict__':
+                return dict(**self)
+
+            return self[name]
+else:
+    from types import SimpleNamespace
+
+
 # Provide access to a configuration file for the active environment.
 
 if MIG_ENV in ('local', 'docker'):
@@ -237,6 +252,9 @@ def assert_over(self, values=None, _AssertOver=AssertOver):
         self._register_check(check_callable)
         return assert_over
 
+    def temppath(self, relative_path, **kwargs):
+        return temppath(relative_path, self, **kwargs)
+
     # custom assertions available for common use
 
     def assertFileContentIdentical(self, file_actual, file_expected):
@@ -295,6 +313,69 @@ def pretty_display_path(absolute_path):
         assert not relative_path.startswith('..')
         return relative_path
 
+    def prepareFixtureAssert(self, fixture_relpath, fixture_format=None):
+        """Prepare to assert a value against a fixture."""
+
+        fixture_data, fixture_path = fixturefile(
+            fixture_relpath, fixture_format)
+        return SimpleNamespace(
+            assertAgainstFixture=lambda val: MigTestCase._assertAgainstFixture(
+                self,
+                fixture_format,
+                fixture_data,
+                fixture_path,
+                value=val
+            ),
+            copy_as_temp=lambda prefix: self._fixture_copy_as_temp(
+                self,
+                fixture_format,
+                fixture_data,
+                fixture_path,
+                prefix=prefix
+            )
+        )
+
+    @staticmethod
+    def _assertAgainstFixture(testcase, fixture_format, fixture_data, fixture_path, value=None):
+        """Compare a value against fixture data ensuring that in the case of
+        failure the location of the fixture is prepended to the diff."""
+
+        assert value is not None
+        originalMaxDiff = testcase.maxDiff
+        testcase.maxDiff = None
+
+        raised_exception = None
+        try:
+            testcase.assertEqual(value, fixture_data)
+        except AssertionError as diffexc:
+            raised_exception = diffexc
+        finally:
+            testcase.maxDiff = originalMaxDiff
+        if raised_exception:
+            message = "value differed from fixture stored at %s\n\n%s" % (
+                _to_display_path(fixture_path), raised_exception)
+            raise AssertionError(message)
+
+    @staticmethod
+    def _fixture_copy_as_temp(testcase, fixture_format, fixture_data, fixture_path, prefix=None):
+        """Copy a fixture to temporary file at the given path prefix."""
+
+        assert prefix is not None
+        fixture_basename = os.path.basename(fixture_path)
+        fixture_name = fixture_basename[0:-len(fixture_format) - 1]
+        normalised_path = fixturefile_normname(fixture_name, prefix=prefix)
+        copied_fixture_file = testcase.temppath(normalised_path)
+        shutil.copyfile(fixture_path, copied_fixture_file)
+        return copied_fixture_file
+
+
+def _to_display_path(value):
+    """Convert a relative path to one to be shown as part of test output."""
+    display_path = os.path.relpath(value, MIG_BASE)
+    if not display_path.startswith('.'):
+        return "./" + display_path
+    return display_path
+
 
 def is_path_within(path, start=None, _msg=None):
     """Check if path is within start directory"""
@@ -316,7 +397,7 @@ def ensure_dirs_exist(absolute_dir):
     return absolute_dir
 
 
-def fixturefile(relative_path, fixture_format=None, include_path=False):
+def fixturefile(relative_path, fixture_format=None):
     """Support function for loading fixtures from their serialised format.
 
     Doing so is a little more involved than it may seem because serialisation
@@ -347,7 +428,7 @@ def fixturefile(relative_path, fixture_format=None, include_path=False):
         raise AssertionError(
             "unsupported fixture format: %s" % (fixture_format,))
 
-    return (data, tmp_path) if include_path else data
+    return data, tmp_path
 
 
 def fixturefile_normname(relative_path, prefix=''):

tests/test_mig_shared_configuration.py

@@ -31,7 +31,7 @@
 import os
 import unittest
 
-from tests.support import MigTestCase, TEST_DATA_DIR, PY2, testmain, fixturefile
+from tests.support import MigTestCase, TEST_DATA_DIR, PY2, testmain
 from mig.shared.configuration import Configuration
 
 
@@ -71,7 +71,7 @@ def test_argument_wwwserve_max_bytes(self):
 
     @unittest.skipIf(PY2, "Python 3 only")
     def test_default_object(self):
-        expected_values = fixturefile(
+        prepared_fixture = self.prepareFixtureAssert(
             'mig_shared_configuration--new', fixture_format='json')
 
         configuration = Configuration(None)
@@ -84,8 +84,7 @@ def test_default_object(self):
 
         actual_values = _to_dict(configuration)
 
-        self.maxDiff = None
-        self.assertEqual(actual_values, expected_values)
+        prepared_fixture.assertAgainstFixture(actual_values)
 
     def test_object_isolation(self):
         configuration_1 = Configuration(None)

tests/test_mig_shared_functionality_cat.py

@@ -35,7 +35,7 @@
 import unittest
 
 from tests.support import MIG_BASE, PY2, TEST_DATA_DIR, MigTestCase, testmain, \
-    fixturefile, fixturefile_normname, ensure_dirs_exist, temppath
+    temppath, ensure_dirs_exist
 
 from mig.shared.base import client_id_dir
 from mig.shared.functionality.cat import _main as submain, main as realmain
@@ -78,13 +78,12 @@ def before_each(self):
 
         conf_user_db_home = ensure_dirs_exist(self.configuration.user_db_home)
         temppath(conf_user_db_home, self)
-        db_fixture, db_fixture_file = fixturefile('MiG-users.db--example',
-                                                  fixture_format='binary',
-                                                  include_path=True)
-        test_db_file = temppath(fixturefile_normname('MiG-users.db--example',
-                                                     prefix=conf_user_db_home),
-                                self)
-        shutil.copyfile(db_fixture_file, test_db_file)
+        prepared_fixture = self.prepareFixtureAssert(
+            'MiG-users.db--example',
+            fixture_format='binary',
+        )
+
+        test_db_file = prepared_fixture.copy_as_temp(prefix=conf_user_db_home)
 
         # create the test user home directory
         self.test_user_dir = ensure_dirs_exist(test_user_dir)