test and fix

2 files changed, 10 insertions, 2 deletions

diff --git a/interface.py b/interface.py
index 78f0afa..325e470 100644
--- a/interface.py
+++ b/interface.py
@@ -59,6 +59,7 @@ def extend(klass, interface, _recurs=False):
             kimplementsklass = type(kimplements)
             kimplements = list(kimplements)
         except AttributeError:
+            kimplementsklass = tuple
             kimplements = []
         kimplements.append(interface)
         klass.__implements__ = kimplementsklass(kimplements)
diff --git a/test/unittest_interface.py b/test/unittest_interface.py
index 22992c3..c708ff5 100644
--- a/test/unittest_interface.py
+++ b/test/unittest_interface.py
@@ -22,6 +22,7 @@ class C2(B):
 class D(C1):
     __implements__ = ()
 
+class Z(object): pass
 
 class ExtendTC(TestCase):
 
@@ -33,8 +34,6 @@ class ExtendTC(TestCase):
         dimpl = D.__implements__
         
     def test_base(self):
-        extend(A, IFace1)
-        self.failUnless(A.__implements__ is aimpl)
         extend(A, IFace2)
         self.failUnlessEqual(A.__implements__, (IFace1, IFace2))  
         self.failUnlessEqual(B.__implements__, (IFace1, IFace2))
@@ -44,6 +43,14 @@ class ExtendTC(TestCase):
         self.failUnless(C2.__implements__ is c2impl)
         self.failUnlessEqual(D.__implements__, (IFace2,))
 
+    def test_already_impl(self):
+        extend(A, IFace1)
+        self.failUnless(A.__implements__ is aimpl)
+
+    def test_no_impl(self):
+        extend(Z, IFace1)
+        self.failUnlessEqual(Z.__implements__, (IFace1,))
+        
     def test_notimpl_explicit(self):
         extend(C1, IFace3)
         self.failUnless(C1.__implements__ is c1impl)