TST: add test_update_raises_without_intersection on DataFrame (pandas…

…-dev#55509).

pandas/core/frame.py

@@ -8788,8 +8788,8 @@ def update(
         rows = other.index.intersection(self.index)
         if rows.empty:
             raise ValueError(
-                "Update not allowed when other has no index in common with "
-                "this dataframe."
+                "Update not allowed when the index on `other` has no intersection "
+                "with this dataframe."
             )
 
         other = other.reindex(rows)

pandas/tests/frame/methods/test_update.py

@@ -222,6 +222,13 @@ def test_update_raises_on_duplicate_argument_index(self):
         with pytest.raises(ValueError, match="duplicate index"):
             df.update(other)
 
+    def test_update_raises_without_intersection(self):
+        # GH#55509
+        df = DataFrame({"a": [1]}, index=[1])
+        other = DataFrame({"a": [2]}, index=[2])
+        with pytest.raises(ValueError, match="no intersection"):
+            df.update(other)
+
     def test_update_on_duplicate_frame_unique_argument_index(self):
         # GH#55509
         df = DataFrame({"a": [1, 1, 1]}, index=[1, 1, 2], dtype=np.dtype("intc"))