Backport PR #57341 on branch 2.2.x (REGR: assert_series_equal defaulting to check_exact=True for Index) (#57380)

Backport PR #57341: REGR: assert_series_equal defaulting to check_exact=True for Index

Co-authored-by: Patrick Hoefler <61934744+phofl@users.noreply.github.com>

Author: meeseeksmachine

doc/source/whatsnew/v2.2.1.rst

@@ -17,6 +17,7 @@ Fixed regressions
 - Fixed performance regression in :meth:`Series.combine_first` (:issue:`55845`)
 - Fixed regression in :func:`concat` changing long-standing behavior that always sorted the non-concatenation axis when the axis was a :class:`DatetimeIndex` (:issue:`57006`)
 - Fixed regression in :func:`merge_ordered` raising ``TypeError`` for ``fill_method="ffill"`` and ``how="left"`` (:issue:`57010`)
+- Fixed regression in :func:`pandas.testing.assert_series_equal` defaulting to ``check_exact=True`` when checking the :class:`Index` (:issue:`57067`)
 - Fixed regression in :func:`wide_to_long` raising an ``AttributeError`` for string columns (:issue:`57066`)
 - Fixed regression in :meth:`.DataFrameGroupBy.idxmin`, :meth:`.DataFrameGroupBy.idxmax`, :meth:`.SeriesGroupBy.idxmin`, :meth:`.SeriesGroupBy.idxmax` ignoring the ``skipna`` argument (:issue:`57040`)
 - Fixed regression in :meth:`.DataFrameGroupBy.idxmin`, :meth:`.DataFrameGroupBy.idxmax`, :meth:`.SeriesGroupBy.idxmin`, :meth:`.SeriesGroupBy.idxmax` where values containing the minimum or maximum value for the dtype could produce incorrect results (:issue:`57040`)

pandas/_testing/asserters.py

@@ -902,6 +902,7 @@ def assert_series_equal(
     >>> tm.assert_series_equal(a, b)
     """
     __tracebackhide__ = True
+    check_exact_index = False if check_exact is lib.no_default else check_exact
     if (
         check_exact is lib.no_default
         and rtol is lib.no_default
@@ -944,7 +945,7 @@ def assert_series_equal(
             right.index,
             exact=check_index_type,
             check_names=check_names,
-            check_exact=check_exact,
+            check_exact=check_exact_index,
             check_categorical=check_categorical,
             check_order=not check_like,
             rtol=rtol,

pandas/tests/util/test_assert_series_equal.py

@@ -474,3 +474,11 @@ def test_assert_series_equal_int_tol():
     tm.assert_extension_array_equal(
         left.astype("Int64").values, right.astype("Int64").values, rtol=1.5
     )
+
+
+def test_assert_series_equal_index_exact_default():
+    # GH#57067
+    ser1 = Series(np.zeros(6, dtype=int), [0, 0.2, 0.4, 0.6, 0.8, 1])
+    ser2 = Series(np.zeros(6, dtype=int), np.linspace(0, 1, 6))
+    tm.assert_series_equal(ser1, ser2)
+    tm.assert_frame_equal(ser1.to_frame(), ser2.to_frame())