Fix liquid tracking in aspirate96, dispense96 (#565)

Co-authored-by: Rick Wierenga <rick_wierenga@icloud.com>

Author: ericguan04

pylabrobot/liquid_handling/liquid_handler.py

@@ -1621,6 +1621,7 @@ async def aspirate96(
           liquids = [(None, volume)]
           all_liquids.append(liquids)
         else:
+          # tracker is enabled: update tracker liquid history
           liquids = well.tracker.remove_liquid(volume=volume)  # type: ignore
           all_liquids.append(liquids)
 
@@ -1760,15 +1761,16 @@ async def dispense96(
       if not len(containers) == 96:
         raise ValueError(f"dispense96 expects 96 wells, got {len(containers)}")
 
-      for channel, well in zip(self.head96.values(), containers):
+      for well, channel in zip(containers, self.head96.values()):
         # even if the volume tracker is disabled, a liquid (None, volume) is added to the list
         # during the aspiration command
         liquids = channel.get_tip().tracker.remove_liquid(volume=volume)
         reversed_liquids = list(reversed(liquids))
         all_liquids.append(reversed_liquids)
 
-        for liquid, vol in reversed_liquids:
-          well.tracker.add_liquid(liquid=liquid, volume=vol)
+        if not well.tracker.is_disabled and does_volume_tracking():
+          for liquid, vol in reversed_liquids:
+            well.tracker.add_liquid(liquid=liquid, volume=vol)
 
       dispense = MultiHeadDispensePlate(
         wells=cast(List[Well], containers),

pylabrobot/liquid_handling/liquid_handler_tests.py

@@ -1091,6 +1091,19 @@ async def error_func(*args, **kwargs):
     # test volume doens't change on failed dispense
     assert self.lh.head[0].get_tip().tracker.get_used_volume() == 200
 
+  async def test_96_head_volume_tracking(self):
+    for item in self.plate.get_all_items():
+      item.tracker.set_liquids([(Liquid.WATER, 10)])
+    await self.lh.pick_up_tips96(self.tip_rack)
+    await self.lh.aspirate96(self.plate, volume=10)
+    for i in range(96):
+      self.assertEqual(self.lh.head96[i].get_tip().tracker.get_used_volume(), 10)
+      self.plate.get_item(i).tracker.get_used_volume() == 0
+    await self.lh.dispense96(self.plate, volume=10)
+    for i in range(96):
+      self.assertEqual(self.lh.head96[i].get_tip().tracker.get_used_volume(), 0)
+      self.plate.get_item(i).tracker.get_used_volume() == 10
+
 
 class TestLiquidHandlerCrossContaminationTracking(unittest.IsolatedAsyncioTestCase):
   async def asyncSetUp(self):