Adjust concat tests for string option (#56446)

Author: phofl

pandas/tests/reshape/concat/test_append_common.py

@@ -57,10 +57,12 @@ class TestConcatAppendCommon:
     Test common dtype coercion rules between concat and append.
     """
 
-    def test_dtypes(self, item, index_or_series):
+    def test_dtypes(self, item, index_or_series, using_infer_string):
         # to confirm test case covers intended dtypes
         typ, vals = item
         obj = index_or_series(vals)
+        if typ == "object" and using_infer_string:
+            typ = "string"
         if isinstance(obj, Index):
             assert obj.dtype == typ
         elif isinstance(obj, Series):

pandas/tests/reshape/concat/test_categorical.py

@@ -51,15 +51,17 @@ def test_categorical_concat(self, sort):
         exp["h"] = exp["h"].astype(df2["h"].dtype)
         tm.assert_frame_equal(res, exp)
 
-    def test_categorical_concat_dtypes(self):
+    def test_categorical_concat_dtypes(self, using_infer_string):
         # GH8143
         index = ["cat", "obj", "num"]
         cat = Categorical(["a", "b", "c"])
         obj = Series(["a", "b", "c"])
         num = Series([1, 2, 3])
         df = pd.concat([Series(cat), obj, num], axis=1, keys=index)
 
-        result = df.dtypes == "object"
+        result = df.dtypes == (
+            object if not using_infer_string else "string[pyarrow_numpy]"
+        )
         expected = Series([False, True, False], index=index)
         tm.assert_series_equal(result, expected)
 

pandas/tests/reshape/concat/test_empty.py

@@ -13,7 +13,7 @@
 
 
 class TestEmptyConcat:
-    def test_handle_empty_objects(self, sort):
+    def test_handle_empty_objects(self, sort, using_infer_string):
         df = DataFrame(
             np.random.default_rng(2).standard_normal((10, 4)), columns=list("abcd")
         )
@@ -26,7 +26,9 @@ def test_handle_empty_objects(self, sort):
         concatted = concat(frames, axis=0, sort=sort)
 
         expected = df.reindex(columns=["a", "b", "c", "d", "foo"])
-        expected["foo"] = expected["foo"].astype("O")
+        expected["foo"] = expected["foo"].astype(
+            object if not using_infer_string else "string[pyarrow_numpy]"
+        )
         expected.loc[0:4, "foo"] = "bar"
 
         tm.assert_frame_equal(concatted, expected)
@@ -275,14 +277,14 @@ def test_concat_empty_dataframe(self):
         expected = DataFrame(columns=["a", "b"])
         tm.assert_frame_equal(result, expected)
 
-    def test_concat_empty_dataframe_different_dtypes(self):
+    def test_concat_empty_dataframe_different_dtypes(self, using_infer_string):
         # 39037
         df1 = DataFrame({"a": [1, 2, 3], "b": ["a", "b", "c"]})
         df2 = DataFrame({"a": [1, 2, 3]})
 
         result = concat([df1[:0], df2[:0]])
         assert result["a"].dtype == np.int64
-        assert result["b"].dtype == np.object_
+        assert result["b"].dtype == np.object_ if not using_infer_string else "string"
 
     def test_concat_to_empty_ea(self):
         """48510 `concat` to an empty EA should maintain type EA dtype."""

pandas/tests/reshape/concat/test_index.py

@@ -447,12 +447,14 @@ def test_concat_index_find_common(self, dtype):
         )
         tm.assert_frame_equal(result, expected)
 
-    def test_concat_axis_1_sort_false_rangeindex(self):
+    def test_concat_axis_1_sort_false_rangeindex(self, using_infer_string):
         # GH 46675
         s1 = Series(["a", "b", "c"])
         s2 = Series(["a", "b"])
         s3 = Series(["a", "b", "c", "d"])
-        s4 = Series([], dtype=object)
+        s4 = Series(
+            [], dtype=object if not using_infer_string else "string[pyarrow_numpy]"
+        )
         result = concat(
             [s1, s2, s3, s4], sort=False, join="outer", ignore_index=False, axis=1
         )
@@ -463,7 +465,7 @@ def test_concat_axis_1_sort_false_rangeindex(self):
                 ["c", np.nan] * 2,
                 [np.nan] * 2 + ["d"] + [np.nan],
             ],
-            dtype=object,
+            dtype=object if not using_infer_string else "string[pyarrow_numpy]",
         )
         tm.assert_frame_equal(
             result, expected, check_index_type=True, check_column_type=True