try another dtype_backend

Signed-off-by: Anatoly Myachev <[email protected]>

modin/tests/pandas/utils.py

@@ -1088,8 +1088,13 @@ def eval_io_from_str(csv_str: str, unique_filename: str, **kwargs):
 
 def create_test_dfs(*args, **kwargs) -> tuple[pd.DataFrame, pandas.DataFrame]:
     post_fn = kwargs.pop("post_fn", lambda df: df)
+    post_fn2 = lambda df: post_fn(df).convert_dtypes(
+        dtype_backend="dtype_backend"
+    )  # noqa: E731
     return tuple(
-        map(post_fn, [pd.DataFrame(*args, **kwargs), pandas.DataFrame(*args, **kwargs)])
+        map(
+            post_fn2, [pd.DataFrame(*args, **kwargs), pandas.DataFrame(*args, **kwargs)]
+        )
     )
 
 
@@ -1103,6 +1108,9 @@ def create_test_series(vals, sort=False, **kwargs) -> tuple[pd.Series, pandas.Se
     if sort:
         modin_series = modin_series.sort_values().reset_index(drop=True)
         pandas_series = pandas_series.sort_values().reset_index(drop=True)
+
+    modin_series = modin_series.convert_dtypes(dtype_backend="dtype_backend")
+    pandas_series = pandas_series.convert_dtypes(dtype_backend="dtype_backend")
     return modin_series, pandas_series