diff --git a/lib/mmCIF_to_biounits.py b/lib/mmCIF_to_biounits.py
index 243ec8c..294b381 100644
--- a/lib/mmCIF_to_biounits.py
+++ b/lib/mmCIF_to_biounits.py
@@ -20,8 +20,11 @@
 # from pdbx.reader.PdbxReader import PdbxReader
 # from pdbx.writer.PdbxWriter import PdbxWriter
 # from pdbx.reader.PdbxContainers import *
+import logging
+LOGGER = logging.getLogger()
 
 def parseOperationExpression(expression: str) :
+    LOGGER.debug('Parsing biounit operation %s',str)
     operations = []
     stops = [ "," , "-" , ")" ]
 
@@ -95,6 +98,9 @@ def prepareOperation(mmcif_dict, op1index, op2index) :
     return operation
 
 def mmCIF_to_biounits(mmcif_dict):
+    """Return a list of mmcif dictionaries for each biounit, and a dictionary of chains copies to new chains"""
+    biounits_as_mmcif_dicts = []
+
     assembly_ids = mmcif_dict.get('_pdbx_struct_assembly_gen.assembly_id',None)
     if not assembly_ids: # We cannot create biounits if there are not assemblies to create
         return []
@@ -115,8 +121,10 @@ def mmCIF_to_biounits(mmcif_dict):
     assert len(atom_site_Cartn_y) == atom_site_count,"Cartn_x entries are missing in the structure"
     assert len(atom_site_Cartn_z) == atom_site_count,"Cartn_x entries are missing in the structure"
 
-    # Create a CIF file for every assembly specified in pdbx_struct_assembly_gen
+    # Create a CIF dictionary for every assembly specified in pdbx_struct_assembly_gen
+    
     for index in range(assembly_count):
+        LOGGER.info("Processing biounit assembly %d of %d",index,assembly_count)
         # Ultimately we want to create transformed lists of atomic coordinates
         # setup numpy matrix to receive  maximum number of calculation results
         # Keep in mind that often many atoms are excluded from biounits
@@ -176,6 +184,7 @@ def mmCIF_to_biounits(mmcif_dict):
 
         # For every operation in the first parenthesized list
         for op1 in oper :
+            LOGGER.debug("op1=%s",str(op1))
             # Find the index of the current operation in the oper_list category table
             op1index = 0
             for row in range(oper_list_count):
@@ -235,10 +244,5 @@ def mmCIF_to_biounits(mmcif_dict):
         # for key in new_mmcif_dict:
         #   if '_atom_site.' in key:
         #      print(key,len(new_mmcif_dict[key]))
-        
-        from Bio.PDB.mmcifio import MMCIFIO
-        io = MMCIFIO()
-        io.set_dict(mmcif_dict)
-        io.save("/tmp/new_rcox.cif")
-        print("Success for now")
-        sys.exit(1)
+        biounits_as_mmcif_dicts.append(new_mmcif_dict)
+    return biounits_as_mmcif_dicts        
diff --git a/lib/tests/test_mmCIF_to_biounits.py b/lib/tests/test_mmCIF_to_biounits.py
index 8963802..8c82845 100755
--- a/lib/tests/test_mmCIF_to_biounits.py
+++ b/lib/tests/test_mmCIF_to_biounits.py
@@ -2,6 +2,7 @@
 """Very specific tests of transcript alignments"""
 
 import pytest
+import sys
 import warnings
 import logging
 import pprint
@@ -9,26 +10,39 @@
 from Bio.PDB import *
 from lib.mmCIF_to_biounits import mmCIF_to_biounits
 
-LOGGER = logging.getLogger()
 # warnings.simplefilter('ignore', PDBConstructionWarning)
 
-def test_mmCIF_to_biounits():
-    """
-    6DWU should return two biounit file
+def exercise_mmCIF_to_biounits(pdb_id):
+    LOGGER.info("Attempting biounit creation for %s"%pdb_id)
+    filename = PDBList().retrieve_pdb_file(pdb_id,file_format='mmCif',pdir='/tmp',overwrite=True)
+    LOGGER.info("Successful download of %s to %s",pdb_id,filename)
+    sys.exit(1)
+    mmcif_parser = MMCIFParser(QUIET=True)
+    structure_6DWU = mmcif_parser.get_structure('pdb',filename)
+    biounits_list= mmCIF_to_biounits(mmcif_parser._mmcif_dict)
+    assert type(biounits_list[0]) == dict
+    LOGGER.info("%d biounits returned for %s",len(biounits_list),pdb_id)
 
-    First, align using the new sifts isoform specific mechanism.
-    Second, aling with biopython Needleman-Wunsch
-    Third, attempt a terrible alignment
-    """
+    # Can we save the biounit???
+    mmcif_io = MMCIFIO()
+    mmcif_io.set_dict(biounits_list[0])
+    mmcif_io.save('/tmp/%s1.cif'%pdb_id)
+    return biounits_list
 
-    # Alignment 1: Sifts isoform specific alignment
-    filename_6DWU = PDBList().retrieve_pdb_file('6DWU',file_format='mmCif',pdir='/tmp',overwrite=True)
-    mmcif_parser = MMCIFParser(QUIET=True)
-    structure_6DWU = mmcif_parser.get_structure('6DWU',filename_6DWU)
-    # import pdb; pdb.set_trace()
-    biounits = mmCIF_to_biounits(mmcif_parser._mmcif_dict)
-    assert len(biounits) == 2,"Two biounits should have been created - but only got %d"%len(biounits)
 
+def test_mmCIF_to_biounits():
+    # biounits_list = exercise_mmCIF_to_biounits('6dw1')
+    # assert len(biounits) == 2,"Two biounits should have been created - but only got %d"%len(biounits)
+
+    biounits_list = exercise_mmCIF_to_biounits('4rkk')
+    assert len(biounits_list) == 1
+    biounits_list = exercise_mmCIF_to_biounits('3c70')
+    assert len(biounits_list) == 1
 
+FORMAT='%(asctime)s %(levelname)-4s [%(filename)16s:%(lineno)d] %(message)s'
+logging.basicConfig(format=FORMAT,level=logging.DEBUG)
+LOGGER = logging.getLogger()
+LOGGER.info("Starting...")
 test_mmCIF_to_biounits() 
 
+