Merge pull request #12153 from tylerjereddy/setdiff1d_test_cov

DOC, TST: cover setdiff1d assume_unique

2 files changed, 11 insertions, 2 deletions

diff --git a/numpy/lib/arraysetops.py b/numpy/lib/arraysetops.py
index 2f8c07114..ec62cd7a6 100644
--- a/numpy/lib/arraysetops.py
+++ b/numpy/lib/arraysetops.py
@@ -738,7 +738,7 @@ def setdiff1d(ar1, ar2, assume_unique=False):
     """
     Find the set difference of two arrays.
 
-    Return the sorted, unique values in `ar1` that are not in `ar2`.
+    Return the unique values in `ar1` that are not in `ar2`.
 
     Parameters
     ----------
@@ -753,7 +753,9 @@ def setdiff1d(ar1, ar2, assume_unique=False):
     Returns
     -------
     setdiff1d : ndarray
-        Sorted 1D array of values in `ar1` that are not in `ar2`.
+        1D array of values in `ar1` that are not in `ar2`. The result
+        is sorted when `assume_unique=False`, but otherwise only sorted
+        if the input is sorted.
 
     See Also
     --------
diff --git a/numpy/lib/tests/test_arraysetops.py b/numpy/lib/tests/test_arraysetops.py
index 4b61726d2..fef06ba53 100644
--- a/numpy/lib/tests/test_arraysetops.py
+++ b/numpy/lib/tests/test_arraysetops.py
@@ -388,6 +388,13 @@ class TestSetOps(object):
         a = np.array((), np.uint32)
         assert_equal(setdiff1d(a, []).dtype, np.uint32)
 
+    def test_setdiff1d_unique(self):
+        a = np.array([3, 2, 1])
+        b = np.array([7, 5, 2])
+        expected = np.array([3, 1])
+        actual = setdiff1d(a, b, assume_unique=True)
+        assert_equal(actual, expected)
+
     def test_setdiff1d_char_array(self):
         a = np.array(['a', 'b', 'c'])
         b = np.array(['a', 'b', 's'])