Add tests of Ellipsis

tests/snippets/ellipsis.py

@@ -13,6 +13,20 @@ assert d is e
 
 assert Ellipsis.__repr__() == 'Ellipsis'
 assert Ellipsis.__reduce__() == 'Ellipsis'
+assert type(Ellipsis).__new__(type(Ellipsis)) == Ellipsis
+assert type(Ellipsis).__reduce__(Ellipsis) == 'Ellipsis'
+try:
+    type(Ellipsis).__new__(type(1))
+except TypeError:
+    pass
+else:
+    assert False, '`Ellipsis.__new__` should only accept `type(Ellipsis)` as argument'
+try:
+    type(Ellipsis).__reduce__(1)
+except TypeError:
+    pass
+else:
+    assert False, '`Ellipsis.__reduce__` should only accept `Ellipsis` as argument'
 
 assert Ellipsis is ...
 Ellipsis = 2