wip feat(psi_pos): (#118) add base with optional signals

tests/test_psi_positioner_base.py

@@ -0,0 +1,27 @@
+from unittest.mock import MagicMock
+
+import pytest
+from ophyd.device import Component as Cpt
+from ophyd.signal import EpicsSignal
+from ophyd.sim import FakeEpicsSignal, FakeEpicsSignalRO
+
+from ophyd_devices.interfaces.base_classes.psi_positioner_base import (
+    PSIPositionerBase,
+    RequiredSignalNotSpecified,
+)
+
+
+def test_cannot_isntantiate_without_required_signals():
+    class PSITestPositionerWOSignal(PSIPositionerBase): ...
+
+    class PSITestPositionerWithSignal(PSIPositionerBase):
+        user_setpoint: EpicsSignal = Cpt(FakeEpicsSignal, ".VAL", limits=True, auto_monitor=True)
+        user_readback = Cpt(FakeEpicsSignalRO, ".RBV", kind="hinted", auto_monitor=True)
+
+    with pytest.raises(RequiredSignalNotSpecified) as e:
+        PSITestPositionerWOSignal("", name="")
+        assert e.match("user_setpoint")
+        assert e.match("user_readback")
+
+    dev = PSITestPositionerWithSignal("", name="")
+    assert dev.user_setpoint.get() == 0