TST: Add a regression test for gh-11216

The test is marked xfail right now as it is not fixed in master

1 files changed, 18 insertions, 1 deletions

diff --git a/numpy/lib/tests/test_arraypad.py b/numpy/lib/tests/test_arraypad.py
index 55c917156..581ae30e5 100644
--- a/numpy/lib/tests/test_arraypad.py
+++ b/numpy/lib/tests/test_arraypad.py
@@ -3,8 +3,11 @@
 """
 from __future__ import division, absolute_import, print_function
 
+import pytest
+
 import numpy as np
-from numpy.testing import (assert_array_equal, assert_raises, assert_allclose,)
+from numpy.testing import (assert_array_equal, assert_raises, assert_allclose,
+                           assert_equal)
 from numpy.lib import pad
 
 
@@ -344,6 +347,20 @@ class TestStatistic(object):
             )
         assert_array_equal(a, b)
 
+    @pytest.mark.parametrize("mode", [
+        pytest.param("mean", marks=pytest.mark.xfail(reason="gh-11216")),
+        "median",
+        "minimum",
+        "maximum"
+    ])
+    def test_same_prepend_append(self, mode):
+        """ Test that appended and prepended values are equal """
+        # This test is constructed to trigger floating point rounding errors in
+        # a way that caused gh-11216 for mode=='mean'
+        a = np.array([-1, 2, -1]) + np.array([0, 1e-12, 0], dtype=np.float64)
+        a = np.pad(a, (1, 1), mode)
+        assert_equal(a[0], a[-1])
+
 
 class TestConstant(object):
     def test_check_constant(self):