Reduce config file IO and date coupling in tests

Tests not directly related to interacting with the file system are often
reading the file during setup. This can lead to longer runtimes in the
case of the duplicate IP loop, and possible test collisions such as in
the configuration check tests. Also, the
tests/inventory/openstack_user_config.yml file is no longer tracked in
repo, and thus it's unnecessary to create a temp file.

This doesn't completely remove file IO integration testing - there is
still a test for the load_user_configuration function. It does, however,
remove file system access for configuration in places where such access
isn't part of the test.

The global _BASE_CONFIG dictionary is populated once, then later
accessed via copies so that 1) the original values are always maintained
2) tests have more assurance they're not getting a mutated dictionary,
either by file or memory access.

Change-Id: Icddb90dedeca347567828f06ea443f4aa7ad69b0

tests/test_inventory.py

@@ -41,8 +41,9 @@ _BASE_CONFIG = {}
 
 
 def get_config():
+    """Return a copy of the original config so original isn't modified."""
     global _BASE_CONFIG
-    return _BASE_CONFIG
+    return copy.deepcopy(_BASE_CONFIG)
 
 
 def make_config():
@@ -52,7 +53,9 @@ def make_config():
     configuration dict  and write them out to a file for consumption by
     the tests.
     """
-    config = get_config()
+    # Allow access here so we can populate the dictionary.
+    global _BASE_CONFIG
+    config = _BASE_CONFIG
 
     files = glob.glob(os.path.join(CONFD, '*.aio'))
     for file_name in files:
@@ -419,8 +422,10 @@ class TestIps(unittest.TestCase):
         # Allow custom assertion errors.
         self.longMessage = True
 
-    def test_duplicates(self):
+    @mock.patch('dynamic_inventory.load_user_configuration')
+    def test_duplicates(self, mock_load_config):
         """Test that no duplicate IPs are made on any network."""
+        mock_load_config.return_value = get_config()
 
         for i in xrange(0, 99):
             # tearDown is ineffective for this loop, so clean the USED_IPs
@@ -461,9 +466,7 @@ class TestIps(unittest.TestCase):
 class TestConfigCheckBase(unittest.TestCase):
     def setUp(self):
         self.config_changed = False
-        self.user_defined_config = dict()
-        with open(USER_CONFIG_FILE, 'rb') as f:
-            self.user_defined_config.update(yaml.safe_load(f.read()) or {})
+        self.user_defined_config = get_config()
 
     def delete_config_key(self, user_defined_config, key):
         try:
@@ -477,7 +480,6 @@ class TestConfigCheckBase(unittest.TestCase):
             self.write_config()
 
     def add_config_key(self, key, value):
-        self.config_changed = True
         self.user_defined_config[key] = value
         self.write_config()
 
@@ -495,21 +497,17 @@ class TestConfigCheckBase(unittest.TestCase):
 
     def write_config(self):
         self.config_changed = True
-        # rename temporarily our user_config_file so we can use the new one
-        os.rename(USER_CONFIG_FILE, USER_CONFIG_FILE + ".tmp")
         # Save new user_config_file
         with open(USER_CONFIG_FILE, 'wb') as f:
             f.write(yaml.dump(self.user_defined_config))
 
     def restore_config(self):
         # get back our initial user config file
-        os.remove(USER_CONFIG_FILE)
-        os.rename(USER_CONFIG_FILE + ".tmp", USER_CONFIG_FILE)
-        self.config_changed = False
+        self.user_defined_config = get_config()
+        self.write_config()
 
     def set_new_hostname(self, user_defined_config, group,
                          old_hostname, new_hostname):
-        self.config_changed = True
         # set a new name for the specified hostname
         old_hostname_settings = user_defined_config[group].pop(old_hostname)
         user_defined_config[group][new_hostname] = old_hostname_settings
@@ -1001,9 +999,7 @@ class TestOverridingEnvVars(OverridingEnvBase):
 class TestOverridingEnvIntegration(OverridingEnvBase):
     def setUp(self):
         super(TestOverridingEnvIntegration, self).setUp()
-        self.user_defined_config = {}
-        with open(USER_CONFIG_FILE, 'rb') as f:
-            self.user_defined_config.update(yaml.safe_load(f.read()))
+        self.user_defined_config = get_config()
 
         # Inventory is necessary since keys are assumed present
         self.inv = di.get_inventory(TARGET_DIR, '')