diff --git a/model_server/base/roiset.py b/model_server/base/roiset.py
index 8b7642774a4e84c9f476b5aa744ec62652ed551e..cfeec9eec6d4de1e2d56a358055140a58893b4a6 100644
--- a/model_server/base/roiset.py
+++ b/model_server/base/roiset.py
@@ -954,7 +954,7 @@ class RoiSet(object):
 
         return interm
 
-    def serialize(self, where: Path, prefix='') -> dict:
+    def serialize(self, where: Path, prefix='roiset') -> dict:
         """
         Export the minimal information needed to recreate RoiSet object, i.e. CSV data file and tight patch masks
         :param where: path of directory in which to write files
diff --git a/model_server/conf/testing.py b/model_server/conf/testing.py
index dd60e586b12407876645381d7867661fa111efd9..85f33a665ec4d7582b52aa871bb1f0e0d8a3038a 100644
--- a/model_server/conf/testing.py
+++ b/model_server/conf/testing.py
@@ -112,8 +112,7 @@ def setup_test_data():
         raise Exception('Could not find test data, try setting environmental variable UNITTEST_DATA_ROOT.')
 
     meta['root'] = Path(root)
-    op_ev = os.environ.get('UNITTEST_OUTPUT', (meta['root'] / 'test_output'))
-    meta['output_path'] = Path(op_ev)
+    meta['output_path'] = meta['root'] / 'test_output'
     meta['output_path'].mkdir(parents=True, exist_ok=True)
 
     # resolve relative paths