clean configuration for testing

This way, unit tests will never see a user's global beets configuration.

beets/__init__.py

@@ -20,4 +20,4 @@ from beets.util import confit
 
 Library = beets.library.Library
 
-config = confit.Configuration('beets', __name__)
+config = confit.Configuration('beets', __name__, False)

beets/ui/__init__.py

@@ -607,10 +607,14 @@ class SubcommandsOptionParser(optparse.OptionParser):
 
 # The root parser and its main function.
 
-def _raw_main(args):
+def _raw_main(args, load_config=True):
     """A helper function for `main` without top-level exception
     handling.
     """
+    # Load global configuration files.
+    if load_config:
+        config.read()
+
     # Get the default subcommands.
     from beets.ui.commands import default_commands
 

test/_common.py

@@ -88,10 +88,12 @@ class TestCase(unittest.TestCase):
     completes. Also provides some additional assertion methods.
     """
     def setUp(self):
-        self.old_sources = copy.deepcopy(beets.config.sources)
+        # A "clean" source list including only the defaults.
+        beets.config.sources = []
+        beets.config.read(user=False, defaults=True)
 
     def tearDown(self):
-        beets.config.sources = self.old_sources
+        pass
 
     def assertExists(self, path):
         self.assertTrue(os.path.exists(path),

test/test_ui.py

@@ -443,9 +443,11 @@ class PrintTest(_common.TestCase):
 
 class AutotagTest(_common.TestCase):
     def setUp(self):
+        super(AutotagTest, self).setUp()
         self.io = _common.DummyIO()
         self.io.install()
     def tearDown(self):
+        super(AutotagTest, self).tearDown()
         self.io.restore()
 
     def _no_candidates_test(self, result):
@@ -506,7 +508,7 @@ class ConfigTest(_common.TestCase):
         if config_yaml:
             config_data = yaml.load(config_yaml, Loader=confit.Loader)
             config.set(config_data)
-        ui._raw_main(args + ['test'])
+        ui._raw_main(args + ['test'], False)
 
     def test_paths_section_respected(self):
         def func(lib, opts, args):