TST: clean-up various tests avoiding CoW issues (#55861)

pandas/tests/frame/indexing/test_indexing.py

@@ -747,11 +747,11 @@ def test_getitem_setitem_float_labels(self, using_array_manager):
         expected = df.iloc[0:2]
         tm.assert_frame_equal(result, expected)
 
-        df.loc[1:2] = 0
+        expected = df.iloc[0:2]
         msg = r"The behavior of obj\[i:j\] with a float-dtype index"
         with tm.assert_produces_warning(FutureWarning, match=msg):
             result = df[1:2]
-        assert (result == 0).all().all()
+        tm.assert_frame_equal(result, expected)
 
         # #2727
         index = Index([1.0, 2.5, 3.5, 4.5, 5.0])

pandas/tests/frame/test_api.py

@@ -217,10 +217,8 @@ def test_with_datetimelikes(self):
 
     def test_deepcopy(self, float_frame):
         cp = deepcopy(float_frame)
-        series = cp["A"]
-        series[:] = 10
-        for idx, value in series.items():
-            assert float_frame["A"][idx] != value
+        cp.loc[0, "A"] = 10
+        assert not float_frame.equals(cp)
 
     def test_inplace_return_self(self):
         # GH 1893

pandas/tests/frame/test_nonunique_indexes.py

@@ -322,15 +322,15 @@ def test_set_value_by_index(self):
 
         df = DataFrame(np.arange(9).reshape(3, 3).T)
         df.columns = list("AAA")
-        expected = df.iloc[:, 2]
+        expected = df.iloc[:, 2].copy()
 
         with tm.assert_produces_warning(warn, match=msg):
             df.iloc[:, 0] = 3
         tm.assert_series_equal(df.iloc[:, 2], expected)
 
         df = DataFrame(np.arange(9).reshape(3, 3).T)
         df.columns = [2, float(2), str(2)]
-        expected = df.iloc[:, 1]
+        expected = df.iloc[:, 1].copy()
 
         with tm.assert_produces_warning(warn, match=msg):
             df.iloc[:, 0] = 3

pandas/tests/indexing/test_scalar.py

@@ -140,7 +140,7 @@ def test_frame_at_with_duplicate_axes(self):
         df = DataFrame(arr, columns=["A", "A"])
 
         result = df.at[0, "A"]
-        expected = df.iloc[0]
+        expected = df.iloc[0].copy()
 
         tm.assert_series_equal(result, expected)
 

pandas/tests/series/indexing/test_setitem.py

@@ -1746,7 +1746,7 @@ def test_setitem_with_bool_indexer():
     # GH#42530
 
     df = DataFrame({"a": [1, 2, 3], "b": [4, 5, 6]})
-    result = df.pop("b")
+    result = df.pop("b").copy()
     result[[True, False, False]] = 9
     expected = Series(data=[9, 5, 6], name="b")
     tm.assert_series_equal(result, expected)