TST: use single-class pattern in test_string.py (#56509)

* TST: use single-class pattern in test_string.py

* mypy fixup

* update pyarrow test

* __future__ import

* mypy fixup

Author: jbrockmendel

pandas/core/arrays/arrow/array.py

@@ -632,6 +632,9 @@ def __invert__(self) -> Self:
         # This is a bit wise op for integer types
         if pa.types.is_integer(self._pa_array.type):
             return type(self)(pc.bit_wise_not(self._pa_array))
+        elif pa.types.is_string(self._pa_array.type):
+            # Raise TypeError instead of pa.ArrowNotImplementedError
+            raise TypeError("__invert__ is not supported for string dtypes")
         else:
             return type(self)(pc.invert(self._pa_array))
 

pandas/tests/extension/test_arrow.py

@@ -753,7 +753,11 @@ def test_EA_types(self, engine, data, dtype_backend, request):
 
     def test_invert(self, data, request):
         pa_dtype = data.dtype.pyarrow_dtype
-        if not (pa.types.is_boolean(pa_dtype) or pa.types.is_integer(pa_dtype)):
+        if not (
+            pa.types.is_boolean(pa_dtype)
+            or pa.types.is_integer(pa_dtype)
+            or pa.types.is_string(pa_dtype)
+        ):
             request.applymarker(
                 pytest.mark.xfail(
                     raises=pa.ArrowNotImplementedError,

pandas/tests/extension/test_string.py

@@ -13,7 +13,10 @@
 be added to the array-specific tests in `pandas/tests/arrays/`.
 
 """
+from __future__ import annotations
+
 import string
+from typing import cast
 
 import numpy as np
 import pytest
@@ -90,7 +93,7 @@ def data_for_grouping(dtype, chunked):
     return maybe_split_array(arr, chunked)
 
 
-class TestDtype(base.BaseDtypeTests):
+class TestStringArray(base.ExtensionTests):
     def test_eq_with_str(self, dtype):
         assert dtype == f"string[{dtype.storage}]"
         super().test_eq_with_str(dtype)
@@ -100,43 +103,25 @@ def test_is_not_string_type(self, dtype):
         # because StringDtype is a string type
         assert is_string_dtype(dtype)
 
-
-class TestInterface(base.BaseInterfaceTests):
     def test_view(self, data, request, arrow_string_storage):
         if data.dtype.storage in arrow_string_storage:
             pytest.skip(reason="2D support not implemented for ArrowStringArray")
         super().test_view(data)
 
-
-class TestConstructors(base.BaseConstructorsTests):
     def test_from_dtype(self, data):
         # base test uses string representation of dtype
         pass
 
-
-class TestReshaping(base.BaseReshapingTests):
     def test_transpose(self, data, request, arrow_string_storage):
         if data.dtype.storage in arrow_string_storage:
             pytest.skip(reason="2D support not implemented for ArrowStringArray")
         super().test_transpose(data)
 
-
-class TestGetitem(base.BaseGetitemTests):
-    pass
-
-
-class TestSetitem(base.BaseSetitemTests):
     def test_setitem_preserves_views(self, data, request, arrow_string_storage):
         if data.dtype.storage in arrow_string_storage:
             pytest.skip(reason="2D support not implemented for ArrowStringArray")
         super().test_setitem_preserves_views(data)
 
-
-class TestIndex(base.BaseIndexTests):
-    pass
-
-
-class TestMissing(base.BaseMissingTests):
     def test_dropna_array(self, data_missing):
         result = data_missing.dropna()
         expected = data_missing[[1]]
@@ -154,51 +139,80 @@ def test_fillna_no_op_returns_copy(self, data):
         assert result is not data
         tm.assert_extension_array_equal(result, data)
 
+    def _get_expected_exception(
+        self, op_name: str, obj, other
+    ) -> type[Exception] | None:
+        if op_name in ["__divmod__", "__rdivmod__"]:
+            if isinstance(obj, pd.Series) and cast(
+                StringDtype, tm.get_dtype(obj)
+            ).storage in [
+                "pyarrow",
+                "pyarrow_numpy",
+            ]:
+                # TODO: re-raise as TypeError?
+                return NotImplementedError
+            elif isinstance(other, pd.Series) and cast(
+                StringDtype, tm.get_dtype(other)
+            ).storage in [
+                "pyarrow",
+                "pyarrow_numpy",
+            ]:
+                # TODO: re-raise as TypeError?
+                return NotImplementedError
+            return TypeError
+        elif op_name in ["__mod__", "__rmod__", "__pow__", "__rpow__"]:
+            if cast(StringDtype, tm.get_dtype(obj)).storage in [
+                "pyarrow",
+                "pyarrow_numpy",
+            ]:
+                return NotImplementedError
+            return TypeError
+        elif op_name in ["__mul__", "__rmul__"]:
+            # Can only multiply strings by integers
+            return TypeError
+        elif op_name in [
+            "__truediv__",
+            "__rtruediv__",
+            "__floordiv__",
+            "__rfloordiv__",
+            "__sub__",
+            "__rsub__",
+        ]:
+            if cast(StringDtype, tm.get_dtype(obj)).storage in [
+                "pyarrow",
+                "pyarrow_numpy",
+            ]:
+                import pyarrow as pa
+
+                # TODO: better to re-raise as TypeError?
+                return pa.ArrowNotImplementedError
+            return TypeError
+
+        return None
 
-class TestReduce(base.BaseReduceTests):
     def _supports_reduction(self, ser: pd.Series, op_name: str) -> bool:
         return (
             op_name in ["min", "max"]
             or ser.dtype.storage == "pyarrow_numpy"  # type: ignore[union-attr]
             and op_name in ("any", "all")
         )
 
-
-class TestMethods(base.BaseMethodsTests):
-    pass
-
-
-class TestCasting(base.BaseCastingTests):
-    pass
-
-
-class TestComparisonOps(base.BaseComparisonOpsTests):
     def _cast_pointwise_result(self, op_name: str, obj, other, pointwise_result):
-        dtype = tm.get_dtype(obj)
-        # error: Item "dtype[Any]" of "dtype[Any] | ExtensionDtype" has no
-        # attribute "storage"
-        if dtype.storage == "pyarrow":  # type: ignore[union-attr]
-            cast_to = "boolean[pyarrow]"
-        elif dtype.storage == "pyarrow_numpy":  # type: ignore[union-attr]
+        dtype = cast(StringDtype, tm.get_dtype(obj))
+        if op_name in ["__add__", "__radd__"]:
+            cast_to = dtype
+        elif dtype.storage == "pyarrow":
+            cast_to = "boolean[pyarrow]"  # type: ignore[assignment]
+        elif dtype.storage == "pyarrow_numpy":
             cast_to = np.bool_  # type: ignore[assignment]
         else:
-            cast_to = "boolean"
+            cast_to = "boolean"  # type: ignore[assignment]
         return pointwise_result.astype(cast_to)
 
     def test_compare_scalar(self, data, comparison_op):
         ser = pd.Series(data)
         self._compare_other(ser, data, comparison_op, "abc")
 
-
-class TestParsing(base.BaseParsingTests):
-    pass
-
-
-class TestPrinting(base.BasePrintingTests):
-    pass
-
-
-class TestGroupBy(base.BaseGroupbyTests):
     @pytest.mark.filterwarnings("ignore:Falling back:pandas.errors.PerformanceWarning")
     def test_groupby_extension_apply(self, data_for_grouping, groupby_apply_op):
         super().test_groupby_extension_apply(data_for_grouping, groupby_apply_op)