Change register to an instance method to bind run to func.

handroll/commands/base.py

@@ -25,13 +25,20 @@ def finish():
 class Command(object):
     """A command class with the minimal interface required for each command."""
 
-    @classmethod
-    def register(cls, parser):
+    name = 'command'
+    description = 'the command description'
+    help = 'the command help'
+
+    def register(self, subparsers):
         """Register required options.
 
-        The provided parser is a subparser from ``subparsers.add_parser``.
+        Commands should invoke this method and use the returned parser to
+        add command specific options.
         """
-        raise NotImplementedError()
+        parser = subparsers.add_parser(
+            self.name, description=self.description, help=self.help)
+        parser.set_defaults(func=self.run)
+        return parser
 
     def run(self, args):
         """Run whatever action the command intends."""

handroll/tests/test_commands.py

@@ -9,9 +9,27 @@
 
 class TestCommand(TestCase):
 
-    def test_register_not_implemented(self):
-        parser = mock.Mock()
-        self.assertRaises(NotImplementedError, Command.register, parser)
+    def test_register_returns_parser(self):
+        subparsers = mock.Mock()
+        expected_parser = mock.Mock()
+        subparsers.add_parser.return_value = expected_parser
+        command = Command()
+        parser = command.register(subparsers)
+        self.assertEqual(expected_parser, parser)
+
+    def test_register_command_attributes(self):
+        subparsers = mock.Mock()
+        command = Command()
+        command.register(subparsers)
+        subparsers.add_parser.assert_called_once_with(
+            'command', description='the command description',
+            help='the command help')
+
+    def test_register_run_as_func(self):
+        subparsers = mock.Mock()
+        command = Command()
+        parser = command.register(subparsers)
+        parser.set_defaults.assert_called_once_with(func=command.run)
 
     def test_run_not_implemented(self):
         args = mock.Mock()