Added a test_add1

2 files changed, 12 insertions, 1 deletions

diff --git a/CHANGES.md b/CHANGES.md
index 3e9bd3f..cbf5be8 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -5,7 +5,7 @@ HISTORY
 
 ## 4.2.1 (2018-01-14)
 
-Fixed a regression breaking IPython and discovered by https://github.com/spapini
+Fixed a regression breaking IPython reported by https://github.com/spapini .
 
 ## 4.2.0 (2018-01-14)
 
diff --git a/src/tests/test.py b/src/tests/test.py
index e5f2ff4..cd99e95 100644
--- a/src/tests/test.py
+++ b/src/tests/test.py
@@ -126,6 +126,17 @@ class ExtraTestCase(unittest.TestCase):
             return method(app)
         catch_config_error(lambda app: None)
 
+    def test_add1(self):
+        # similar to what IPython is doing in traitlets.config.application
+        @decorator
+        def add(func, const=1, *args, **kwargs):
+            return const + func(*args, **kwargs)
+
+        def f(x):
+            return x
+        self.assertEqual(add(f)(0), 1)
+        self.assertEqual(add(f, 2)(0), 2)
+
 # ################### test dispatch_on ############################# #
 # adapted from test_functools in Python 3.5
 singledispatch = dispatch_on('obj')