raise if no gripper attached

api/src/opentrons/protocol_engine/commands/unsafe/unsafe_ungrip_labware.py

@@ -1,6 +1,7 @@
 """Ungrip labware payload, result, and implementaiton."""
 
 from __future__ import annotations
+from opentrons.protocol_engine.errors.exceptions import GripperNotAttachedError
 from pydantic import BaseModel
 from typing import Optional, Type
 from typing_extensions import Literal
@@ -42,7 +43,10 @@ async def execute(
         self, params: UnsafeUngripLabwareParams
     ) -> SuccessData[UnsafeUngripLabwareResult, None]:
         """Ungrip Labware."""
+        print("ungripping")
         ot3_hardware_api = ensure_ot3_hardware(self._hardware_api)
+        if not ot3_hardware_api.has_gripper():
+            raise GripperNotAttachedError("No gripper found for ungrip.")
         await ot3_hardware_api.ungrip()
         return SuccessData(public=UnsafeUngripLabwareResult(), private=None)
 

api/tests/opentrons/protocol_engine/commands/unsafe/test_ungrip_labware.py

@@ -7,22 +7,37 @@
     UnsafeUngripLabwareImplementation,
 )
 from opentrons.protocol_engine.commands.command import SuccessData
+from opentrons.protocol_engine.errors.exceptions import GripperNotAttachedError
 from opentrons.protocol_engine.execution import GantryMover
 from opentrons.protocol_engine.types import MotorAxis
 from opentrons.hardware_control import OT3HardwareControlAPI
 from opentrons.hardware_control.types import Axis
+import pytest
 
 
-async def test_engage_axes_implementation(
-    decoy: Decoy, ot3_hardware_api: OT3HardwareControlAPI, gantry_mover: GantryMover
+async def test_ungrip_labware_implementation(
+    decoy: Decoy, ot3_hardware_api: OT3HardwareControlAPI
 ) -> None:
-    """Test EngageAxes command execution."""
+    """Test UngripLabware command execution."""
     subject = UnsafeUngripLabwareImplementation(hardware_api=ot3_hardware_api)
 
+    decoy.when(ot3_hardware_api.has_gripper()).then_return(True)
+
     result = await subject.execute(params=UnsafeUngripLabwareParams())
 
     assert result == SuccessData(public=UnsafeUngripLabwareResult(), private=None)
 
     decoy.verify(
         await ot3_hardware_api.ungrip(),
     )
+
+
+async def test_ungrip_labware_implementation_raises_no_gripper_attached(
+    decoy: Decoy, ot3_hardware_api: OT3HardwareControlAPI
+) -> None:
+    """Test UngripLabware command execution."""
+    subject = UnsafeUngripLabwareImplementation(hardware_api=ot3_hardware_api)
+
+    decoy.when(ot3_hardware_api.has_gripper()).then_return(False)
+    with pytest.raises(GripperNotAttachedError):
+        await subject.execute(params=UnsafeUngripLabwareParams())