Put plugin options into separate argparse groups

tests/unit/test_option_manager.py

@@ -307,3 +307,14 @@ def test_optparse_normalize_help(optmanager, capsys):
     out, err = capsys.readouterr()
     output = out + err
     assert 'default: bar' in output
+
+
+def test_optmanager_group(optmanager, capsys):
+    """Test that group(...) causes options to be assigned to a group."""
+    with optmanager.group('groupname'):
+        optmanager.add_option('--foo')
+    with pytest.raises(SystemExit):
+        optmanager.parse_args(['--help'])
+    out, err = capsys.readouterr()
+    output = out + err
+    assert '\ngroupname:\n' in output

tests/unit/test_plugin.py

@@ -5,6 +5,7 @@ import mock
 import pytest
 
 from flake8 import exceptions
+from flake8.options import manager as options_manager
 from flake8.plugins import manager
 
 
@@ -91,7 +92,7 @@ def test_register_options():
     entry_point = mock.Mock(spec=['load'])
     plugin_obj = mock.Mock(spec_set=['name', 'version', 'add_options',
                                      'parse_options'])
-    option_manager = mock.Mock(spec=['register_plugin'])
+    option_manager = mock.MagicMock(spec=options_manager.OptionManager)
     plugin = manager.Plugin('T000', entry_point)
     plugin._plugin = plugin_obj