Corrected references to test dataset

tests/base/test_roiset.py

@@ -529,7 +529,7 @@ class TestRoiSetSerialization(unittest.TestCase):
         self.stack = generate_file_accessor(data['multichannel_zstack_raw']['path'])
         self.stack_ch_pa = self.stack.get_mono(params['segmentation_channel'])
         self.seg_mask_3d = generate_file_accessor(data['multichannel_zstack_mask3d']['path'])
-        self.seg_mask_2d = generate_file_accessor(roiset_test_data['multichannel_zstack']['mask_path'])
+        self.seg_mask_2d = generate_file_accessor(data['multichannel_zstack_raw']['path'])
 
     @staticmethod
     def _label_is_2d(id_map, la):  # single label's zmask has same counts as its MIP