CLN: fix numpy FutureWarning in tests (#41414)

Author: fangchenli

pandas/tests/arithmetic/test_object.py

@@ -311,7 +311,7 @@ def test_sub_object(self):
             index - "foo"
 
         with pytest.raises(TypeError, match=msg):
-            index - np.array([2, "foo"])
+            index - np.array([2, "foo"], dtype=object)
 
     def test_rsub_object(self):
         # GH#19369

pandas/tests/dtypes/test_inference.py

@@ -1042,7 +1042,7 @@ def test_infer_dtype_datetime64_with_na(self, na_value):
             np.array([np.datetime64("2011-01-01"), Timestamp("2011-01-02")]),
             np.array([Timestamp("2011-01-02"), np.datetime64("2011-01-01")]),
             np.array([np.nan, Timestamp("2011-01-02"), 1.1]),
-            np.array([np.nan, "2011-01-01", Timestamp("2011-01-02")]),
+            np.array([np.nan, "2011-01-01", Timestamp("2011-01-02")], dtype=object),
             np.array([np.datetime64("nat"), np.timedelta64(1, "D")], dtype=object),
             np.array([np.timedelta64(1, "D"), np.datetime64("nat")], dtype=object),
         ],

pandas/tests/test_common.py

@@ -163,6 +163,5 @@ def test_serializable(obj):
 class TestIsBoolIndexer:
     def test_non_bool_array_with_na(self):
         # in particular, this should not raise
-        arr = np.array(["A", "B", np.nan])
-
+        arr = np.array(["A", "B", np.nan], dtype=object)
         assert not com.is_bool_indexer(arr)

pandas/tests/tools/test_to_datetime.py

@@ -1899,7 +1899,10 @@ def test_to_datetime_infer_datetime_format_inconsistent_format(self, cache):
     @pytest.mark.parametrize("cache", [True, False])
     def test_to_datetime_infer_datetime_format_series_with_nans(self, cache):
         s = Series(
-            np.array(["01/01/2011 00:00:00", np.nan, "01/03/2011 00:00:00", np.nan])
+            np.array(
+                ["01/01/2011 00:00:00", np.nan, "01/03/2011 00:00:00", np.nan],
+                dtype=object,
+            )
         )
         tm.assert_series_equal(
             to_datetime(s, infer_datetime_format=False, cache=cache),
@@ -1916,7 +1919,8 @@ def test_to_datetime_infer_datetime_format_series_start_with_nans(self, cache):
                     "01/01/2011 00:00:00",
                     "01/02/2011 00:00:00",
                     "01/03/2011 00:00:00",
-                ]
+                ],
+                dtype=object,
             )
         )
 

pandas/tests/util/test_hashing.py

@@ -90,7 +90,7 @@ def test_hash_array(series):
 
 
 @pytest.mark.parametrize(
-    "arr2", [np.array([3, 4, "All"]), np.array([3, 4, "All"], dtype=object)]
+    "arr2", [np.array([3, 4, "All"], dtype="U"), np.array([3, 4, "All"], dtype=object)]
 )
 def test_hash_array_mixed(arr2):
     result1 = hash_array(np.array(["3", "4", "All"]))