TST: raising ValueError when inserting one dataframe in another (#42831)

* TST: raising ValueError when inserting one dataframe in another

* added GH issue reference

* rev msg

* included both msgs

* updated

* Update test_insert.py

* Update test_insert.py

* Update test_insert.py

pandas/tests/frame/indexing/test_insert.py

@@ -89,3 +89,13 @@ def test_insert_item_cache(self, using_array_manager):
         ser.values[0] = 99
 
         assert df.iloc[0, 0] == df[0][0]
+
+    def test_insert_frame(self):
+        # GH#42403
+        df = DataFrame({"col1": [1, 2], "col2": [3, 4]})
+        msg = (
+            "Expected a 1D array, got an array with shape "
+            r"\(2, 2\)|Wrong number of items passed 2, placement implies 1"
+        )
+        with pytest.raises(ValueError, match=msg):
+            df.insert(1, "newcol", df)