diff --git a/tests/devices/unit_tests/test_smargon.py b/tests/devices/unit_tests/test_smargon.py
new file mode 100644
index 0000000000..03c60d89d9
--- /dev/null
+++ b/tests/devices/unit_tests/test_smargon.py
@@ -0,0 +1,66 @@
+from time import sleep
+from typing import Tuple
+
+import pytest
+from ophyd.sim import make_fake_device
+
+from dodal.devices.smargon import Smargon, StubPosition
+
+
+@pytest.fixture
+def smargon() -> Smargon:
+    return make_fake_device(Smargon)(name="smargon")
+
+
+def set_smargon_pos(smargon: Smargon, pos: Tuple[float, float, float]):
+    smargon.x.user_readback.sim_put(pos[0])
+    smargon.y.user_readback.sim_put(pos[1])
+    smargon.z.user_readback.sim_put(pos[2])
+
+
+def test_given_to_robot_disp_low_when_stub_offsets_set_to_robot_load_then_proc_set(
+    smargon: Smargon,
+):
+    smargon.stub_offsets.to_robot_load.disp.sim_put(0)
+
+    status = smargon.stub_offsets.set(StubPosition.RESET_TO_ROBOT_LOAD)
+    status.wait()
+
+    assert smargon.stub_offsets.to_robot_load.proc.get() == 1
+    assert smargon.stub_offsets.center_at_current_position.proc.get() == 0
+
+
+def test_given_center_disp_low_and_at_centre_when_stub_offsets_set_to_center_then_proc_set(
+    smargon: Smargon,
+):
+    smargon.stub_offsets.center_at_current_position.disp.sim_put(0)
+    set_smargon_pos(smargon, (0, 0, 0))
+
+    status = smargon.stub_offsets.set(StubPosition.CURRENT_AS_CENTER)
+    status.wait()
+
+    assert smargon.stub_offsets.to_robot_load.proc.get() == 0
+    assert smargon.stub_offsets.center_at_current_position.proc.get() == 1
+
+
+def test_given_center_disp_low_when_stub_offsets_set_to_center_and_moved_to_0_0_0_then_proc_set(
+    smargon: Smargon,
+):
+    smargon.stub_offsets.center_at_current_position.disp.sim_put(0)
+
+    set_smargon_pos(smargon, (1.5, 0.5, 3.4))
+
+    status = smargon.stub_offsets.set(StubPosition.CURRENT_AS_CENTER)
+
+    sleep(0.01)
+
+    assert smargon.stub_offsets.center_at_current_position.proc.get() == 1
+
+    assert not status.done
+
+    set_smargon_pos(smargon, (0, 0, 0))
+
+    status.wait()
+
+    assert smargon.stub_offsets.to_robot_load.proc.get() == 0
+    assert smargon.stub_offsets.center_at_current_position.proc.get() == 1