Add pandas string dtypes to legacy pickle tests.

Author: Liam3851

pandas/compat/pickle_compat.py

@@ -17,6 +17,7 @@
 from pandas._libs.arrays import NDArrayBacked
 from pandas._libs.tslibs import BaseOffset
 
+from pandas.core.api import StringDtype
 from pandas.core.arrays import (
     DatetimeArray,
     PeriodArray,

pandas/tests/io/data/legacy_pickle/1.5.3/1.5.3_x86_64_win_3.11.13.pickle

@@ -147,6 +147,7 @@ def create_pickle_data():
         "float": Index(np.arange(10, dtype=np.float64)),
         "uint": Index(np.arange(10, dtype=np.uint64)),
         "timedelta": timedelta_range("00:00:00", freq="30min", periods=10),
+        "string": Index(["foo", "bar", "baz", "qux", "quux"], dtype='string'),
     }
 
     index["range"] = RangeIndex(10)
@@ -185,6 +186,7 @@ def create_pickle_data():
         "dt": Series(date_range("20130101", periods=5)),
         "dt_tz": Series(date_range("20130101", periods=5, tz="US/Eastern")),
         "period": Series([Period("2000Q1")] * 5),
+        "string": Series(["foo", "bar", "baz", "qux", "quux"], dtype="string"),
     }
 
     mixed_dup_df = DataFrame(data)
@@ -233,6 +235,12 @@ def create_pickle_data():
             },
             index=range(5),
         ),
+        "string": DataFrame(
+            {
+                "A": Series(["foo", "bar", "baz", "qux", "quux"], dtype="string"),
+                "B": Series(["one", "two", "one", "two", "three"], dtype="string"),
+            }
+        )
     }
 
     cat = {