TST: Additions/updates to tests (#56822)

* A test for Future warning in the applymap_index method of the style class

* Minor modification changig pd.Dataframe to Dataframe

* Minor modification in matching message

* changed the apply_index method to  applymap_index

* Minor formatting adding extra space

* Removed the docstring

* modified the function passed into the the function been tested

pandas/tests/io/formats/style/test_style.py

@@ -1586,3 +1586,15 @@ def test_output_buffer(mi_styler, format):
     # gh 47053
     with tm.ensure_clean(f"delete_me.{format}") as f:
         getattr(mi_styler, f"to_{format}")(f)
+
+
+def test_deprecation_warning_for_usage_of_aaply_map_index_method_of_styler_object():
+    # 56717 https://github.com/pandas-dev/pandas/issues/56717
+    df = DataFrame([[1, 2], [3, 4]], index=["A", "B"])
+    msg = "Styler.applymap_index has been deprecated. Use Styler.map_index instead."
+
+    def color_b(s):
+        return "background-color:yellow;"
+
+    with tm.assert_produces_warning(FutureWarning, match=msg):
+        df.style.applymap_index(color_b, axis="columns")