chore: increase local test coverage to 100 (#379)

tests/frame/test_common.py

@@ -355,6 +355,15 @@ def test_cross_join(df_raw: Any, expected: dict[str, list[Any]]) -> None:
         df.join(df, how="cross", left_on="a")  # type: ignore[arg-type]
 
 
+def test_cross_join_non_pandas() -> None:
+    df = nw.from_native(df_pandas).select("a")
+    # HACK to force testing for a non-pandas codepath
+    df._dataframe._implementation = "modin"
+    result = df.join(df, how="cross")  # type: ignore[arg-type]
+    expected = {"a": [1, 1, 1, 3, 3, 3, 2, 2, 2], "a_right": [1, 3, 2, 1, 3, 2, 1, 3, 2]}
+    compare_dicts(result, expected)
+
+
 @pytest.mark.parametrize(
     "df_raw", [df_pandas, df_lazy, df_pandas_nullable, df_pandas_pyarrow]
 )