Fis reset tweaks in test not applying to field_metadata in Metadata objects

src/calibre/db/tests/base.py

@@ -24,8 +24,6 @@ class BaseTest(unittest.TestCase):
     def setUp(self):
         from calibre.utils.recycle_bin import nuke_recycle
         nuke_recycle()
-        from calibre.utils.config_base import reset_tweaks_to_default
-        reset_tweaks_to_default()
         self.library_path = self.mkdtemp()
         self.create_db(self.library_path)
 

src/calibre/db/tests/main.py

@@ -18,6 +18,10 @@ def find_tests():
     return unittest.defaultTestLoader.discover(os.path.dirname(os.path.abspath(__file__)), pattern='*.py')
 
 if __name__ == '__main__':
+    from calibre.utils.config_base import reset_tweaks_to_default
+    from calibre.ebooks.metadata.book.base import reset_field_metadata
+    reset_tweaks_to_default()
+    reset_field_metadata()
     parser = argparse.ArgumentParser()
     parser.add_argument('name', nargs='?', default=None,
                         help='The name of the test to run, for e.g. writing.WritingTest.many_many_basic or .many_many_basic for a shortcut')

src/calibre/ebooks/metadata/book/base.py

@@ -42,6 +42,10 @@ NULL_VALUES = {
 
 field_metadata = FieldMetadata()
 
+def reset_field_metadata():
+    global field_metadata
+    field_metadata = FieldMetadata()
+
 ck = lambda typ: icu_lower(typ).strip().replace(':', '').replace(',', '')
 cv = lambda val: val.strip().replace(',', '|').replace(':', '|')