TST: Add tests for NAT comparison FutureWarning.

The behavior of NAT comparisons will change in Numpy 1.13. Make sure
that a FutureWarning is emitted when the results will change.

1 files changed, 28 insertions, 0 deletions

diff --git a/numpy/core/tests/test_datetime.py b/numpy/core/tests/test_datetime.py
index 8aeaf51ac..601f09c09 100644
--- a/numpy/core/tests/test_datetime.py
+++ b/numpy/core/tests/test_datetime.py
@@ -1086,6 +1086,34 @@ class TestDateTime(TestCase):
         assert_equal(np.greater(a, b), [0, 1, 0, 1, 0])
         assert_equal(np.greater_equal(a, b), [1, 1, 0, 1, 0])
 
+    def test_datetime_compare_nat(self):
+        dt_nat = np.datetime64('NaT', 'D')
+        dt_other = np.datetime64('2000-01-01')
+        td_nat = np.timedelta64('NaT', 'h')
+        td_other = np.timedelta64(1, 'h')
+
+        for op in [np.equal, np.less, np.less_equal,
+                   np.greater, np.greater_equal]:
+            if op(dt_nat, dt_nat):
+                assert_warns(FutureWarning, op, dt_nat, dt_nat)
+            if op(dt_nat, dt_other):
+                assert_warns(FutureWarning, op, dt_nat, dt_other)
+            if op(dt_other, dt_nat):
+                assert_warns(FutureWarning, op, dt_other, dt_nat)
+            if op(td_nat, td_nat):
+                assert_warns(FutureWarning, op, td_nat, td_nat)
+            if op(td_nat, td_other):
+                assert_warns(FutureWarning, op, td_nat, td_other)
+            if op(td_other, td_nat):
+                assert_warns(FutureWarning, op, td_other, td_nat)
+
+        assert_warns(FutureWarning, np.not_equal, dt_nat, dt_nat)
+        assert_(np.not_equal(dt_nat, dt_other))
+        assert_(np.not_equal(dt_other, dt_nat))
+        assert_warns(FutureWarning, np.not_equal, td_nat, td_nat)
+        assert_(np.not_equal(td_nat, td_other))
+        assert_(np.not_equal(td_other, td_nat))
+
     def test_datetime_minmax(self):
         # The metadata of the result should become the GCD
         # of the operand metadata