TST: add test for warning

jklymak · jklymak · commit 03b3d2814501 · 2020-06-23T17:16:02.000-07:00
diff --git a/lib/matplotlib/tests/test_dates.py b/lib/matplotlib/tests/test_dates.py
@@ -947,3 +947,16 @@ def test_change_epoch():
     np.testing.assert_allclose(
         mdates.date2num(np.datetime64('1970-01-01T12:00:00')),
         0.5)
+
+
+def test_warn_notintervals():
+    dates = np.arange('2001-01-10', '2001-03-04', dtype='datetime64[D]')
+    locator = mdates.AutoDateLocator(interval_multiples=False)
+    locator.intervald[3] = [2]
+    locator.create_dummy_axis()
+    locator.set_view_interval(mdates.date2num(dates[0]),
+                              mdates.date2num(dates[-1]))
+    with pytest.warns(UserWarning) as rec:
+        locs = locator()
+        assert len(rec) == 1
+        assert "AutoDateLocator was unable" in str(rec[0].message)
