1 files changed, 18 insertions, 3 deletions
diff --git a/numpy/testing/_private/utils.py b/numpy/testing/_private/utils.py
index 67b7d317c..2842eb147 100644
--- a/numpy/testing/_private/utils.py
+++ b/numpy/testing/_private/utils.py
@@ -284,7 +284,7 @@ def assert_equal(actual, desired, err_msg='', verbose=True):
     the scalar.
 
     This function handles NaN comparisons as if NaN was a "normal" number.
-    That is, no assertion is raised if both objects have NaNs in the same
+    That is, AssertionError is not raised if both objects have NaNs in the same
     positions.  This is in contrast to the IEEE standard on NaNs, which says
     that NaN compared to anything must return False.
 
@@ -1609,6 +1609,12 @@ def assert_array_max_ulp(a, b, maxulp=1, dtype=None):
     AssertionError
         If one or more elements differ by more than `maxulp`.
 
+    Notes
+    -----
+    For computing the ULP difference, this API does not differentiate between
+    various representations of NAN (ULP difference between 0x7fc00000 and 0xffc00000
+    is zero.
+
     See Also
     --------
     assert_array_almost_equal_nulp : Compare two arrays relatively to their
@@ -1649,6 +1655,12 @@ def nulp_diff(x, y, dtype=None):
         number of representable floating point numbers between each item in x
         and y.
 
+    Notes
+    -----
+    For computing the ULP difference, this API does not differentiate between
+    various representations of NAN (ULP difference between 0x7fc00000 and 0xffc00000
+    is zero.
+
     Examples
     --------
     # By definition, epsilon is the smallest number such as 1 + eps != 1, so
@@ -1668,8 +1680,11 @@ def nulp_diff(x, y, dtype=None):
     if np.iscomplexobj(x) or np.iscomplexobj(y):
         raise NotImplementedError("_nulp not implemented for complex array")
 
-    x = np.array(x, dtype=t)
-    y = np.array(y, dtype=t)
+    x = np.array([x], dtype=t)
+    y = np.array([y], dtype=t)
+
+    x[np.isnan(x)] = np.nan
+    y[np.isnan(y)] = np.nan
 
     if not x.shape == y.shape:
         raise ValueError("x and y do not have the same shape: %s - %s" %