Fix missing raise in Probe.set_contact_ids() size validation

src/probeinterface/probe.py

@@ -570,14 +570,15 @@ def set_contact_ids(self, contact_ids: np.array | list):
             self._contact_ids = None
             return
 
-        assert np.unique(contact_ids).size == contact_ids.size, "Contact ids have to be unique within a Probe"
-
         if contact_ids.size != self.get_contact_count():
-            ValueError(
+            raise ValueError(
                 f"contact_ids {contact_ids.size} do not have the same size "
                 f"as number of contacts {self.get_contact_count()}"
             )
 
+        if np.unique(contact_ids).size != contact_ids.size:
+            raise ValueError("contact_ids must be unique within a Probe")
+
         if contact_ids.dtype.kind != "U":
             contact_ids = contact_ids.astype("U")
 

tests/test_probegroup.py

@@ -92,6 +92,30 @@ def test_probegroup_allows_duplicate_positions_across_probes():
     assert len(group.probes) == 2
 
 
+def test_set_contact_ids_rejects_within_probe_duplicates():
+    """Setting duplicate contact_ids within a single probe raises ValueError."""
+    from probeinterface import Probe
+
+    positions = np.array([[0, 0], [10, 10]])
+    probe = Probe(ndim=2, si_units="um")
+    probe.set_contacts(positions=positions, shapes="circle", shape_params={"radius": 5})
+
+    with pytest.raises(ValueError, match="unique within a Probe"):
+        probe.set_contact_ids(["a", "a"])
+
+
+def test_set_contact_ids_rejects_wrong_size():
+    """Setting contact_ids with wrong count raises ValueError."""
+    from probeinterface import Probe
+
+    positions = np.array([[0, 0], [10, 10]])
+    probe = Probe(ndim=2, si_units="um")
+    probe.set_contacts(positions=positions, shapes="circle", shape_params={"radius": 5})
+
+    with pytest.raises(ValueError, match="do not have the same size"):
+        probe.set_contact_ids(["a", "b", "c"])
+
+
 if __name__ == "__main__":
     test_probegroup()
     # ~ test_probegroup_3d()