Extend MigTestCase with such that it can provide a configuration object.

A great deal of code that we wish to exercise under test requires a
configuration object. The wiring to generate test configuration values
is already in tree, but actually consuming it in tests was done in an
ad-hoc fashion. Meanwhile the separate notion of a FakeConfiguration
was added primarily to allow exercising code that needs a specific
subset of vars set with specific values.

This patch raises this use-case to the level of the common support
library. Use the way a logger was exposed as a blueprint and add a
configuration property to MigTestCase - this is a computed property
that lazily creates a (by default) FakeConfiguration object.

This object persists for the duration of the test. Provide a means for
easily overriding this to make it a fully populated Configuration
instance using the testconfig - this mechanism is _declarative_ such
that the details of configuration loading are transparent to callers.
Document this use via an extra test case in the support library tests.

Author: albu-diku

tests/support/__init__.py

@@ -40,6 +40,7 @@
 import sys
 from unittest import TestCase, main as testmain
 
+from tests.support.configsupp import FakeConfiguration
 from tests.support.suppconst import MIG_BASE, TEST_BASE, TEST_FIXTURE_DIR, \
     TEST_OUTPUT_DIR
 
@@ -48,6 +49,20 @@
 # force defaults to a local environment
 os.environ['MIG_ENV'] = 'local'
 
+# expose the configuraed environment as a constant
+MIG_ENV = os.environ['MIG_ENV']
+
+if MIG_ENV == 'local':
+    # force testconfig as the conig file path
+    is_py2 = PY2
+    _conf_dir_suffix = "-py%s" % ('2' if is_py2 else '3',)
+    _conf_dir = "testconfs%s" % (_conf_dir_suffix,)
+    _local_conf = os.path.join(
+        MIG_BASE, 'envhelp/output', _conf_dir, 'MiGserver.conf')
+    _config_file = os.getenv('MIG_CONF', None)
+    if _config_file is None:
+        os.environ['MIG_CONF'] = _local_conf
+
 # All MiG related code will at some point include bits from the mig module
 # namespace. Rather than have this knowledge spread through every test file,
 # make the sole responsbility of test files to find the support file and
@@ -103,6 +118,7 @@ def __init__(self, *args):
         super(MigTestCase, self).__init__(*args)
         self._cleanup_checks = list()
         self._cleanup_paths = set()
+        self._configuration = None
         self._logger = None
         self._skip_logging = False
 
@@ -153,6 +169,31 @@ def _reset_logging(self, stream):
         root_handler = root_logger.handlers[0]
         root_handler.stream = stream
 
+    # testcase defaults
+
+    @staticmethod
+    def _make_configuration_instance(configuration_to_make):
+        if configuration_to_make == 'fakeconfig':
+            return FakeConfiguration()
+        elif configuration_to_make == 'testconfig':
+            from mig.shared.conf import get_configuration_object
+            return get_configuration_object(skip_log=True, disable_auth_log=True)
+        else:
+            raise AssertionError(
+                "MigTestCase: unknown configuration %r" % (configuration_to_make,))
+
+    def _provide_configuration(self):
+        return 'fakeconfig'
+
+    @property
+    def configuration(self):
+        """Init a fake configuration if not already done"""
+        if self._configuration is None:
+            configuration_to_make = self._provide_configuration()
+            self._configuration = self._make_configuration_instance(
+                configuration_to_make)
+        return self._configuration
+
     @property
     def logger(self):
         """Init a fake logger if not already done"""
@@ -199,6 +240,10 @@ def assertPathExists(self, relative_path):
         assert not os.path.isabs(
             relative_path), "expected relative path within output folder"
         absolute_path = os.path.join(TEST_OUTPUT_DIR, relative_path)
+        return MigTestCase._absolute_path_kind(absolute_path)
+
+    @staticmethod
+    def _absolute_path_kind(absolute_path):
         stat_result = os.lstat(absolute_path)
         if stat.S_ISLNK(stat_result.st_mode):
             return "symlink"

tests/test_support.py

@@ -4,7 +4,10 @@
 import unittest
 
 from tests.support import MigTestCase, PY2, testmain, temppath, \
-                    AssertOver
+    AssertOver, FakeConfiguration
+
+from mig.shared.conf import get_configuration_object
+from mig.shared.configuration import Configuration
 
 
 class InstrumentedAssertOver(AssertOver):
@@ -39,6 +42,17 @@ def _class_attribute(self, name, **kwargs):
         else:
             return getattr(cls, name, None)
 
+    def test_provides_a_fake_configuration(self):
+        configuration = self.configuration
+
+        self.assertIsInstance(configuration, FakeConfiguration)
+
+    def test_provides_a_fake_configuration_for_the_duration_of_the_test(self):
+        c1 = self.configuration
+        c2 = self.configuration
+
+        self.assertIs(c2, c1)
+
     @unittest.skipIf(PY2, "Python 3 only")
     def test_unclosed_files_are_recorded(self):
         tmp_path = temppath("support-unclosed", self)
@@ -88,5 +102,23 @@ def test_when_asserting_over_multiple_values_after(self):
         self.assertTrue(attempt_wrapper.was_check_callable_called())
 
 
+class SupportTestCase_overridden_configuration(MigTestCase):
+    def _provide_configuration(self):
+        return 'testconfig'
+
+    def test_provides_the_test_configuration(self):
+        expected_last_dir = 'testconfs-py2' if PY2 else 'testconfs-py3'
+
+        configuration = self.configuration
+
+        # check we have a real config object
+        self.assertIsInstance(configuration, Configuration)
+        # check for having loaded a config file from a test config dir
+        config_file_path_parts = configuration.config_file.split(os.path.sep)
+        config_file_path_parts.pop()  # discard file part
+        config_file_last_dir = config_file_path_parts.pop()
+        self.assertTrue(config_file_last_dir, expected_last_dir)
+
+
 if __name__ == '__main__':
     testmain()