numpy
diff --git a/‎doc/release/upcoming_changes/19857.improvement.rst
Lines changed: 12 additions & 7 deletions b/‎doc/release/upcoming_changes/19857.improvement.rst
Lines changed: 12 additions & 7 deletions
diff --git a/‎numpy/core/tests/test_deprecations.py
Lines changed: 20 additions & 0 deletions b/‎numpy/core/tests/test_deprecations.py
Lines changed: 20 additions & 0 deletions
@@ -1,8 +1,13 @@
-Add new linear interpolation methods for ``quantile`` and ``percentile``
-------------------------------------------------------------------------
+Add new methods for ``quantile`` and ``percentile``
+---------------------------------------------------
 
-``quantile`` and ``percentile`` now have 13 linear interpolation methods,
-nine of which can be found in the scientific literature.
-The remaining methods are NumPy specific and are kept for backwards
-compatibility. The default is "inclusive" (method 7), whose behavior is equivalent
-to the former default "linear".
+``quantile`` and ``percentile`` now have have a ``method=``
+keyword argument supporting 13 different methods.
+This replaces the ``interpolation=`` keyword argument.
+
+The methods are now aligned with nine methods which can be
+found in scientific literature and the R language.
+The remaining methods are the previous discontinuous variations
+of the default "linear" one.
+
+Please see the documentation of `numpy.percentile` for more information.
@@ -1230,3 +1230,23 @@ def test_deprecated_module(self):
     def test_deprecated_attr(self):
         finfo = np.finfo(float)
         self.assert_deprecated(lambda: getattr(finfo, "machar"))
+
+
+class TestQuantileInterpolationDeprecation(_DeprecationTestCase):
+    # Deprecated 2021-11-08, NumPy 1.22
+    @pytest.mark.parametrize("func",
+        [np.percentile, np.quantile, np.nanpercentile, np.nanquantile])
+    def test_deprecated(self, func):
+        self.assert_deprecated(
+            lambda: func([0., 1.], 0., interpolation="linear"))
+        self.assert_deprecated(
+            lambda: func([0., 1.], 0., interpolation="nearest"))
+
+    @pytest.mark.parametrize("func",
+            [np.percentile, np.quantile, np.nanpercentile, np.nanquantile])
+    def test_both_passed(self, func):
+        with warnings.catch_warnings():
+            # catch the DeprecationWarning so that it does not raise:
+            warnings.simplefilter("always", DeprecationWarning)
+            with pytest.raises(TypeError):
+                func([0., 1.], 0., interpolation="nearest", method="nearest")