DOC: Fix Wald docstring

Fix Wald Docstring to reflect actual restriction on parameters
Add a test to ensure these are enforced for scalar inputs

2 files changed, 4 insertions, 2 deletions

diff --git a/numpy/random/mtrand/mtrand.pyx b/numpy/random/mtrand/mtrand.pyx
index c5e4662d4..5f1039cb2 100644
--- a/numpy/random/mtrand/mtrand.pyx
+++ b/numpy/random/mtrand/mtrand.pyx
@@ -3530,9 +3530,9 @@ cdef class RandomState:
         Parameters
         ----------
         mean : float or array_like of floats
-            Distribution mean, should be > 0.
+            Distribution mean, must be > 0.
         scale : float or array_like of floats
-            Scale parameter, should be >= 0.
+            Scale parameter, must be > 0.
         size : int or tuple of ints, optional
             Output shape.  If the given shape is, e.g., ``(m, n, k)``, then
             ``m * n * k`` samples are drawn.  If size is ``None`` (default),
diff --git a/numpy/random/tests/test_random.py b/numpy/random/tests/test_random.py
index d4721bc62..656e38dc8 100644
--- a/numpy/random/tests/test_random.py
+++ b/numpy/random/tests/test_random.py
@@ -1354,6 +1354,8 @@ class TestBroadcast(object):
         assert_array_almost_equal(actual, desired, decimal=14)
         assert_raises(ValueError, wald, bad_mean, scale * 3)
         assert_raises(ValueError, wald, mean, bad_scale * 3)
+        assert_raises(ValueError, wald, 0.0, 1)
+        assert_raises(ValueError, wald, 0.5, 0.0)
 
     def test_triangular(self):
         left = [1]