Updates for CR: frame and array equality checks, whatsnew.

Author: jmcomie

doc/source/whatsnew/v1.3.2.rst

@@ -23,6 +23,7 @@ Fixed regressions
 - Fixed regression where :meth:`pandas.read_csv` raised a ``ValueError`` when parameters ``names`` and ``prefix`` were both set to None (:issue:`42387`)
 - Fixed regression in comparisons between :class:`Timestamp` object and ``datetime64`` objects outside the implementation bounds for nanosecond ``datetime64`` (:issue:`42794`)
 - Fixed regression in :meth:`.Styler.highlight_min` and :meth:`.Styler.highlight_max` where ``pandas.NA`` was not successfully ignored (:issue:`42650`)
+- Fixed regression in :meth:`pandas.concat` where copy=False was not honored in ``axis=1`` Series concatenation. (:issue:42501).
 
 .. ---------------------------------------------------------------------------
 

pandas/tests/frame/methods/test_astype.py

@@ -751,5 +751,8 @@ def construct_array_type(cls):
 
 def test_frame_astype_no_copy():
     # GH 42501
-    df = DataFrame({"col": [1, 4, None, 5]}, dtype=object)
-    df = df.astype({"col": Int16DtypeNoCopy()}, copy=False)
+    df = DataFrame({"a": [1, 4, None, 5], "b": [6, 7, 8, 9]}, dtype=object)
+    result = df.astype({"a": Int16DtypeNoCopy()}, copy=False)
+
+    tm.assert_frame_equal(df, result, check_dtype=False)
+    tm.assert_numpy_array_equal(df.b.values, result.b.values, check_same="same")