Begin adding tests for the Legacy API

tests/unit/test_legacy_api.py

@@ -0,0 +1,22 @@
+"""Tests for Flake8's legacy API."""
+import mock
+
+from flake8.api import legacy as api
+
+
+def test_get_style_guide():
+    """Verify the methods called on our internal Application."""
+    mockedapp = mock.Mock()
+    with mock.patch('flake8.main.application.Application') as Application:
+        Application.return_value = mockedapp
+        style_guide = api.get_style_guide()
+
+    Application.assert_called_once_with()
+    mockedapp.find_plugins.assert_called_once_with()
+    mockedapp.register_plugin_options.assert_called_once_with()
+    mockedapp.parse_configuration_and_cli.assert_called_once_with([])
+    mockedapp.make_formatter.assert_called_once_with()
+    mockedapp.make_notifier.assert_called_once_with()
+    mockedapp.make_guide.assert_called_once_with()
+    mockedapp.make_file_checker_manager.assert_called_once_with()
+    assert isinstance(style_guide, api.StyleGuide)