Add argument parsing test cases

tests/test_cli.py

@@ -5,8 +5,47 @@
 import logging
 
 from unittest import TestCase
+from StringIO import StringIO
 
-from rabbithole.cli import configure_logging
+import yaml
+
+from mock import patch
+from rabbithole.cli import (
+    configure_logging,
+    parse_arguments,
+)
+
+
+class TestParseArguments(TestCase):
+
+    """Argument parsing test cases."""
+
+    def test_systemexit_raised_on_config_file_does_not_exist(self):
+        """SystemExit is raised if the configuration file does not exist."""
+        # Do not include error output in test output
+        with self.assertRaises(SystemExit), patch('rabbithole.cli.sys.stderr'):
+            parse_arguments(['file-does-not-exist'])
+
+    def test_systemexit_raised_on_config_file_invalid(self):
+        """SystemExit is raised if the configuration file is invalid."""
+        with self.assertRaises(SystemExit), \
+                patch('rabbithole.cli.sys.stderr'), \
+                patch('rabbithole.cli.os') as os, \
+                patch('rabbithole.cli.open') as open:
+            os.path.isfile.return_value = True
+            open().__enter__.return_value = StringIO('>invalid yaml<')
+            parse_arguments(['some file'])
+
+    def test_config_file_load_success(self):
+        """Config file successfully loaded."""
+        expected_value = {'a': 'value'}
+        with patch('rabbithole.cli.os') as os, \
+                patch('rabbithole.cli.open') as open:
+            os.path.isfile.return_value = True
+            open().__enter__.return_value = StringIO(yaml.dump(expected_value))
+            args = parse_arguments(['some file'])
+
+        self.assertDictEqual(args.config, expected_value)
 
 
 class TestConfigureLogging(TestCase):