test: itertools.chain evaluate lazliy
@@ -50,6 +50,12 @@ assert next(x) == 'b'
with assert_raises(TypeError):
next(x)
+# iterables are lazily evaluted
+x = chain.from_iterable(itertools.repeat(range(2)))
+assert next(x) == 0
+assert next(x) == 1
+assert next(x) == 0
+assert next(x) == 1
# itertools.count tests
