adding a simple test for directional_link

IPython/utils/tests/test_traitlets.py

@@ -1,1235 +1,1301 b''
 # encoding: utf-8
 """Tests for IPython.utils.traitlets."""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 # 
 # Adapted from enthought.traits, Copyright (c) Enthought, Inc.,
 # also under the terms of the Modified BSD License.
 
 import pickle
 import re
 import sys
 from unittest import TestCase
 
 import nose.tools as nt
 from nose import SkipTest
 
 from IPython.utils.traitlets import (
     HasTraits, MetaHasTraits, TraitType, Any, CBytes, Dict,
     Int, Long, Integer, Float, Complex, Bytes, Unicode, TraitError,
     Undefined, Type, This, Instance, TCPAddress, List, Tuple,
-    ObjectName, DottedObjectName, CRegExp, link, EventfulList, EventfulDict
+    ObjectName, DottedObjectName, CRegExp, link, directional_link,
+    EventfulList, EventfulDict
 )
 from IPython.utils import py3compat
 from IPython.testing.decorators import skipif
 
 #-----------------------------------------------------------------------------
 # Helper classes for testing
 #-----------------------------------------------------------------------------
 
 
 class HasTraitsStub(HasTraits):
 
     def _notify_trait(self, name, old, new):
         self._notify_name = name
         self._notify_old = old
         self._notify_new = new
 
 
 #-----------------------------------------------------------------------------
 # Test classes
 #-----------------------------------------------------------------------------
 
 
 class TestTraitType(TestCase):
 
     def test_get_undefined(self):
         class A(HasTraits):
             a = TraitType
         a = A()
         self.assertEqual(a.a, Undefined)
 
     def test_set(self):
         class A(HasTraitsStub):
             a = TraitType
 
         a = A()
         a.a = 10
         self.assertEqual(a.a, 10)
         self.assertEqual(a._notify_name, 'a')
         self.assertEqual(a._notify_old, Undefined)
         self.assertEqual(a._notify_new, 10)
 
     def test_validate(self):
         class MyTT(TraitType):
             def validate(self, inst, value):
                 return -1
         class A(HasTraitsStub):
             tt = MyTT
 
         a = A()
         a.tt = 10
         self.assertEqual(a.tt, -1)
 
     def test_default_validate(self):
         class MyIntTT(TraitType):
             def validate(self, obj, value):
                 if isinstance(value, int):
                     return value
                 self.error(obj, value)
         class A(HasTraits):
             tt = MyIntTT(10)
         a = A()
         self.assertEqual(a.tt, 10)
 
         # Defaults are validated when the HasTraits is instantiated
         class B(HasTraits):
             tt = MyIntTT('bad default')
         self.assertRaises(TraitError, B)
 
     def test_is_valid_for(self):
         class MyTT(TraitType):
             def is_valid_for(self, value):
                 return True
         class A(HasTraits):
             tt = MyTT
 
         a = A()
         a.tt = 10
         self.assertEqual(a.tt, 10)
 
     def test_value_for(self):
         class MyTT(TraitType):
             def value_for(self, value):
                 return 20
         class A(HasTraits):
             tt = MyTT
 
         a = A()
         a.tt = 10
         self.assertEqual(a.tt, 20)
 
     def test_info(self):
         class A(HasTraits):
             tt = TraitType
         a = A()
         self.assertEqual(A.tt.info(), 'any value')
 
     def test_error(self):
         class A(HasTraits):
             tt = TraitType
         a = A()
         self.assertRaises(TraitError, A.tt.error, a, 10)
 
     def test_dynamic_initializer(self):
         class A(HasTraits):
             x = Int(10)
             def _x_default(self):
                 return 11
         class B(A):
             x = Int(20)
         class C(A):
             def _x_default(self):
                 return 21
 
         a = A()
         self.assertEqual(a._trait_values, {})
         self.assertEqual(list(a._trait_dyn_inits.keys()), ['x'])
         self.assertEqual(a.x, 11)
         self.assertEqual(a._trait_values, {'x': 11})
         b = B()
         self.assertEqual(b._trait_values, {'x': 20})
         self.assertEqual(list(a._trait_dyn_inits.keys()), ['x'])
         self.assertEqual(b.x, 20)
         c = C()
         self.assertEqual(c._trait_values, {})
         self.assertEqual(list(a._trait_dyn_inits.keys()), ['x'])
         self.assertEqual(c.x, 21)
         self.assertEqual(c._trait_values, {'x': 21})
         # Ensure that the base class remains unmolested when the _default
         # initializer gets overridden in a subclass.
         a = A()
         c = C()
         self.assertEqual(a._trait_values, {})
         self.assertEqual(list(a._trait_dyn_inits.keys()), ['x'])
         self.assertEqual(a.x, 11)
         self.assertEqual(a._trait_values, {'x': 11})
 
 
 
 class TestHasTraitsMeta(TestCase):
 
     def test_metaclass(self):
         self.assertEqual(type(HasTraits), MetaHasTraits)
 
         class A(HasTraits):
             a = Int
 
         a = A()
         self.assertEqual(type(a.__class__), MetaHasTraits)
         self.assertEqual(a.a,0)
         a.a = 10
         self.assertEqual(a.a,10)
 
         class B(HasTraits):
             b = Int()
 
         b = B()
         self.assertEqual(b.b,0)
         b.b = 10
         self.assertEqual(b.b,10)
 
         class C(HasTraits):
             c = Int(30)
 
         c = C()
         self.assertEqual(c.c,30)
         c.c = 10
         self.assertEqual(c.c,10)
 
     def test_this_class(self):
         class A(HasTraits):
             t = This()
             tt = This()
         class B(A):
             tt = This()
             ttt = This()
         self.assertEqual(A.t.this_class, A)
         self.assertEqual(B.t.this_class, A)
         self.assertEqual(B.tt.this_class, B)
         self.assertEqual(B.ttt.this_class, B)
 
 class TestHasTraitsNotify(TestCase):
 
     def setUp(self):
         self._notify1 = []
         self._notify2 = []
 
     def notify1(self, name, old, new):
         self._notify1.append((name, old, new))
 
     def notify2(self, name, old, new):
         self._notify2.append((name, old, new))
 
     def test_notify_all(self):
 
         class A(HasTraits):
             a = Int
             b = Float
 
         a = A()
         a.on_trait_change(self.notify1)
         a.a = 0
         self.assertEqual(len(self._notify1),0)
         a.b = 0.0
         self.assertEqual(len(self._notify1),0)
         a.a = 10
         self.assertTrue(('a',0,10) in self._notify1)
         a.b = 10.0
         self.assertTrue(('b',0.0,10.0) in self._notify1)
         self.assertRaises(TraitError,setattr,a,'a','bad string')
         self.assertRaises(TraitError,setattr,a,'b','bad string')
         self._notify1 = []
         a.on_trait_change(self.notify1,remove=True)
         a.a = 20
         a.b = 20.0
         self.assertEqual(len(self._notify1),0)
 
     def test_notify_one(self):
 
         class A(HasTraits):
             a = Int
             b = Float
 
         a = A()
         a.on_trait_change(self.notify1, 'a')
         a.a = 0
         self.assertEqual(len(self._notify1),0)
         a.a = 10
         self.assertTrue(('a',0,10) in self._notify1)
         self.assertRaises(TraitError,setattr,a,'a','bad string')
 
     def test_subclass(self):
 
         class A(HasTraits):
             a = Int
 
         class B(A):
             b = Float
 
         b = B()
         self.assertEqual(b.a,0)
         self.assertEqual(b.b,0.0)
         b.a = 100
         b.b = 100.0
         self.assertEqual(b.a,100)
         self.assertEqual(b.b,100.0)
 
     def test_notify_subclass(self):
 
         class A(HasTraits):
             a = Int
 
         class B(A):
             b = Float
 
         b = B()
         b.on_trait_change(self.notify1, 'a')
         b.on_trait_change(self.notify2, 'b')
         b.a = 0
         b.b = 0.0
         self.assertEqual(len(self._notify1),0)
         self.assertEqual(len(self._notify2),0)
         b.a = 10
         b.b = 10.0
         self.assertTrue(('a',0,10) in self._notify1)
         self.assertTrue(('b',0.0,10.0) in self._notify2)
 
     def test_static_notify(self):
 
         class A(HasTraits):
             a = Int
             _notify1 = []
             def _a_changed(self, name, old, new):
                 self._notify1.append((name, old, new))
 
         a = A()
         a.a = 0
         # This is broken!!!
         self.assertEqual(len(a._notify1),0)
         a.a = 10
         self.assertTrue(('a',0,10) in a._notify1)
 
         class B(A):
             b = Float
             _notify2 = []
             def _b_changed(self, name, old, new):
                 self._notify2.append((name, old, new))
 
         b = B()
         b.a = 10
         b.b = 10.0
         self.assertTrue(('a',0,10) in b._notify1)
         self.assertTrue(('b',0.0,10.0) in b._notify2)
 
     def test_notify_args(self):
 
         def callback0():
             self.cb = ()
         def callback1(name):
             self.cb = (name,)
         def callback2(name, new):
             self.cb = (name, new)
         def callback3(name, old, new):
             self.cb = (name, old, new)
 
         class A(HasTraits):
             a = Int
 
         a = A()
         a.on_trait_change(callback0, 'a')
         a.a = 10
         self.assertEqual(self.cb,())
         a.on_trait_change(callback0, 'a', remove=True)
 
         a.on_trait_change(callback1, 'a')
         a.a = 100
         self.assertEqual(self.cb,('a',))
         a.on_trait_change(callback1, 'a', remove=True)
 
         a.on_trait_change(callback2, 'a')
         a.a = 1000
         self.assertEqual(self.cb,('a',1000))
         a.on_trait_change(callback2, 'a', remove=True)
 
         a.on_trait_change(callback3, 'a')
         a.a = 10000
         self.assertEqual(self.cb,('a',1000,10000))
         a.on_trait_change(callback3, 'a', remove=True)
 
         self.assertEqual(len(a._trait_notifiers['a']),0)
 
     def test_notify_only_once(self):
 
         class A(HasTraits):
             listen_to = ['a']
             
             a = Int(0)
             b = 0
             
             def __init__(self, **kwargs):
                 super(A, self).__init__(**kwargs)
                 self.on_trait_change(self.listener1, ['a'])
             
             def listener1(self, name, old, new):
                 self.b += 1
 
         class B(A):
                     
             c = 0
             d = 0
             
             def __init__(self, **kwargs):
                 super(B, self).__init__(**kwargs)
                 self.on_trait_change(self.listener2)
             
             def listener2(self, name, old, new):
                 self.c += 1
             
             def _a_changed(self, name, old, new):
                 self.d += 1
 
         b = B()
         b.a += 1
         self.assertEqual(b.b, b.c)
         self.assertEqual(b.b, b.d)
         b.a += 1
         self.assertEqual(b.b, b.c)
         self.assertEqual(b.b, b.d)
 
 
 class TestHasTraits(TestCase):
 
     def test_trait_names(self):
         class A(HasTraits):
             i = Int
             f = Float
         a = A()
         self.assertEqual(sorted(a.trait_names()),['f','i'])
         self.assertEqual(sorted(A.class_trait_names()),['f','i'])
 
     def test_trait_metadata(self):
         class A(HasTraits):
             i = Int(config_key='MY_VALUE')
         a = A()
         self.assertEqual(a.trait_metadata('i','config_key'), 'MY_VALUE')
 
     def test_traits(self):
         class A(HasTraits):
             i = Int
             f = Float
         a = A()
         self.assertEqual(a.traits(), dict(i=A.i, f=A.f))
         self.assertEqual(A.class_traits(), dict(i=A.i, f=A.f))
 
     def test_traits_metadata(self):
         class A(HasTraits):
             i = Int(config_key='VALUE1', other_thing='VALUE2')
             f = Float(config_key='VALUE3', other_thing='VALUE2')
             j = Int(0)
         a = A()
         self.assertEqual(a.traits(), dict(i=A.i, f=A.f, j=A.j))
         traits = a.traits(config_key='VALUE1', other_thing='VALUE2')
         self.assertEqual(traits, dict(i=A.i))
 
         # This passes, but it shouldn't because I am replicating a bug in
         # traits.
         traits = a.traits(config_key=lambda v: True)
         self.assertEqual(traits, dict(i=A.i, f=A.f, j=A.j))
 
     def test_init(self):
         class A(HasTraits):
             i = Int()
             x = Float()
         a = A(i=1, x=10.0)
         self.assertEqual(a.i, 1)
         self.assertEqual(a.x, 10.0)
 
     def test_positional_args(self):
         class A(HasTraits):
             i = Int(0)
             def __init__(self, i):
                 super(A, self).__init__()
                 self.i = i
         
         a = A(5)
         self.assertEqual(a.i, 5)
         # should raise TypeError if no positional arg given
         self.assertRaises(TypeError, A)
 
 #-----------------------------------------------------------------------------
 # Tests for specific trait types
 #-----------------------------------------------------------------------------
 
 
 class TestType(TestCase):
 
     def test_default(self):
 
         class B(object): pass
         class A(HasTraits):
             klass = Type
 
         a = A()
         self.assertEqual(a.klass, None)
 
         a.klass = B
         self.assertEqual(a.klass, B)
         self.assertRaises(TraitError, setattr, a, 'klass', 10)
 
     def test_value(self):
 
         class B(object): pass
         class C(object): pass
         class A(HasTraits):
             klass = Type(B)
 
         a = A()
         self.assertEqual(a.klass, B)
         self.assertRaises(TraitError, setattr, a, 'klass', C)
         self.assertRaises(TraitError, setattr, a, 'klass', object)
         a.klass = B
 
     def test_allow_none(self):
 
         class B(object): pass
         class C(B): pass
         class A(HasTraits):
             klass = Type(B, allow_none=False)
 
         a = A()
         self.assertEqual(a.klass, B)
         self.assertRaises(TraitError, setattr, a, 'klass', None)
         a.klass = C
         self.assertEqual(a.klass, C)
 
     def test_validate_klass(self):
 
         class A(HasTraits):
             klass = Type('no strings allowed')
 
         self.assertRaises(ImportError, A)
 
         class A(HasTraits):
             klass = Type('rub.adub.Duck')
 
         self.assertRaises(ImportError, A)
 
     def test_validate_default(self):
 
         class B(object): pass
         class A(HasTraits):
             klass = Type('bad default', B)
 
         self.assertRaises(ImportError, A)
 
         class C(HasTraits):
             klass = Type(None, B, allow_none=False)
 
         self.assertRaises(TraitError, C)
 
     def test_str_klass(self):
 
         class A(HasTraits):
             klass = Type('IPython.utils.ipstruct.Struct')
 
         from IPython.utils.ipstruct import Struct
         a = A()
         a.klass = Struct
         self.assertEqual(a.klass, Struct)
 
         self.assertRaises(TraitError, setattr, a, 'klass', 10)
 
     def test_set_str_klass(self):
 
         class A(HasTraits):
             klass = Type()
 
         a = A(klass='IPython.utils.ipstruct.Struct')
         from IPython.utils.ipstruct import Struct
         self.assertEqual(a.klass, Struct)
 
 class TestInstance(TestCase):
 
     def test_basic(self):
         class Foo(object): pass
         class Bar(Foo): pass
         class Bah(object): pass
 
         class A(HasTraits):
             inst = Instance(Foo)
 
         a = A()
         self.assertTrue(a.inst is None)
         a.inst = Foo()
         self.assertTrue(isinstance(a.inst, Foo))
         a.inst = Bar()
         self.assertTrue(isinstance(a.inst, Foo))
         self.assertRaises(TraitError, setattr, a, 'inst', Foo)
         self.assertRaises(TraitError, setattr, a, 'inst', Bar)
         self.assertRaises(TraitError, setattr, a, 'inst', Bah())
 
     def test_default_klass(self):
         class Foo(object): pass
         class Bar(Foo): pass
         class Bah(object): pass
 
         class FooInstance(Instance):
             klass = Foo
 
         class A(HasTraits):
             inst = FooInstance()
 
         a = A()
         self.assertTrue(a.inst is None)
         a.inst = Foo()
         self.assertTrue(isinstance(a.inst, Foo))
         a.inst = Bar()
         self.assertTrue(isinstance(a.inst, Foo))
         self.assertRaises(TraitError, setattr, a, 'inst', Foo)
         self.assertRaises(TraitError, setattr, a, 'inst', Bar)
         self.assertRaises(TraitError, setattr, a, 'inst', Bah())
 
     def test_unique_default_value(self):
         class Foo(object): pass
         class A(HasTraits):
             inst = Instance(Foo,(),{})
 
         a = A()
         b = A()
         self.assertTrue(a.inst is not b.inst)
 
     def test_args_kw(self):
         class Foo(object):
             def __init__(self, c): self.c = c
         class Bar(object): pass
         class Bah(object):
             def __init__(self, c, d):
                 self.c = c; self.d = d
 
         class A(HasTraits):
             inst = Instance(Foo, (10,))
         a = A()
         self.assertEqual(a.inst.c, 10)
 
         class B(HasTraits):
             inst = Instance(Bah, args=(10,), kw=dict(d=20))
         b = B()
         self.assertEqual(b.inst.c, 10)
         self.assertEqual(b.inst.d, 20)
 
         class C(HasTraits):
             inst = Instance(Foo)
         c = C()
         self.assertTrue(c.inst is None)
 
     def test_bad_default(self):
         class Foo(object): pass
 
         class A(HasTraits):
             inst = Instance(Foo, allow_none=False)
 
         self.assertRaises(TraitError, A)
 
     def test_instance(self):
         class Foo(object): pass
 
         def inner():
             class A(HasTraits):
                 inst = Instance(Foo())
 
         self.assertRaises(TraitError, inner)
 
 
 class TestThis(TestCase):
 
     def test_this_class(self):
         class Foo(HasTraits):
             this = This
 
         f = Foo()
         self.assertEqual(f.this, None)
         g = Foo()
         f.this = g
         self.assertEqual(f.this, g)
         self.assertRaises(TraitError, setattr, f, 'this', 10)
 
     def test_this_inst(self):
         class Foo(HasTraits):
             this = This()
 
         f = Foo()
         f.this = Foo()
         self.assertTrue(isinstance(f.this, Foo))
 
     def test_subclass(self):
         class Foo(HasTraits):
             t = This()
         class Bar(Foo):
             pass
         f = Foo()
         b = Bar()
         f.t = b
         b.t = f
         self.assertEqual(f.t, b)
         self.assertEqual(b.t, f)
 
     def test_subclass_override(self):
         class Foo(HasTraits):
             t = This()
         class Bar(Foo):
             t = This()
         f = Foo()
         b = Bar()
         f.t = b
         self.assertEqual(f.t, b)
         self.assertRaises(TraitError, setattr, b, 't', f)
 
 class TraitTestBase(TestCase):
     """A best testing class for basic trait types."""
 
     def assign(self, value):
         self.obj.value = value
 
     def coerce(self, value):
         return value
 
     def test_good_values(self):
         if hasattr(self, '_good_values'):
             for value in self._good_values:
                 self.assign(value)
                 self.assertEqual(self.obj.value, self.coerce(value))
 
     def test_bad_values(self):
         if hasattr(self, '_bad_values'):
             for value in self._bad_values:
                 try:
                     self.assertRaises(TraitError, self.assign, value)
                 except AssertionError:
                     assert False, value
 
     def test_default_value(self):
         if hasattr(self, '_default_value'):
             self.assertEqual(self._default_value, self.obj.value)
 
     def test_allow_none(self):
         if (hasattr(self, '_bad_values') and hasattr(self, '_good_values') and
         None in self._bad_values):
             trait=self.obj.traits()['value']
             try:
                 trait.allow_none = True
                 self._bad_values.remove(None)
                 #skip coerce. Allow None casts None to None.
                 self.assign(None)
                 self.assertEqual(self.obj.value,None)
                 self.test_good_values()
                 self.test_bad_values()
             finally:
                 #tear down
                 trait.allow_none = False
                 self._bad_values.append(None)
 
     def tearDown(self):
         # restore default value after tests, if set
         if hasattr(self, '_default_value'):
             self.obj.value = self._default_value
 
 
 class AnyTrait(HasTraits):
 
     value = Any
 
 class AnyTraitTest(TraitTestBase):
 
     obj = AnyTrait()
 
     _default_value = None
     _good_values   = [10.0, 'ten', u'ten', [10], {'ten': 10},(10,), None, 1j]
     _bad_values    = []
 
 
 class IntTrait(HasTraits):
 
     value = Int(99)
 
 class TestInt(TraitTestBase):
 
     obj = IntTrait()
     _default_value = 99
     _good_values   = [10, -10]
     _bad_values    = ['ten', u'ten', [10], {'ten': 10},(10,), None, 1j,
                       10.1, -10.1, '10L', '-10L', '10.1', '-10.1', u'10L',
                       u'-10L', u'10.1', u'-10.1',  '10', '-10', u'10', u'-10']
     if not py3compat.PY3:
         _bad_values.extend([long(10), long(-10), 10*sys.maxint, -10*sys.maxint])
 
 
 class LongTrait(HasTraits):
 
     value = Long(99 if py3compat.PY3 else long(99))
 
 class TestLong(TraitTestBase):
 
     obj = LongTrait()
 
     _default_value = 99 if py3compat.PY3 else long(99)
     _good_values   = [10, -10]
     _bad_values    = ['ten', u'ten', [10], {'ten': 10},(10,),
                       None, 1j, 10.1, -10.1, '10', '-10', '10L', '-10L', '10.1',
                       '-10.1', u'10', u'-10', u'10L', u'-10L', u'10.1',
                       u'-10.1']
     if not py3compat.PY3:
         # maxint undefined on py3, because int == long
         _good_values.extend([long(10), long(-10), 10*sys.maxint, -10*sys.maxint])
         _bad_values.extend([[long(10)], (long(10),)])
 
     @skipif(py3compat.PY3, "not relevant on py3")
     def test_cast_small(self):
         """Long casts ints to long"""
         self.obj.value = 10
         self.assertEqual(type(self.obj.value), long)
 
 
 class IntegerTrait(HasTraits):
     value = Integer(1)
 
 class TestInteger(TestLong):
     obj = IntegerTrait()
     _default_value = 1
 
     def coerce(self, n):
         return int(n)
 
     @skipif(py3compat.PY3, "not relevant on py3")
     def test_cast_small(self):
         """Integer casts small longs to int"""
         if py3compat.PY3:
             raise SkipTest("not relevant on py3")
 
         self.obj.value = long(100)
         self.assertEqual(type(self.obj.value), int)
 
 
 class FloatTrait(HasTraits):
 
     value = Float(99.0)
 
 class TestFloat(TraitTestBase):
 
     obj = FloatTrait()
 
     _default_value = 99.0
     _good_values   = [10, -10, 10.1, -10.1]
     _bad_values    = ['ten', u'ten', [10], {'ten': 10},(10,), None,
                       1j, '10', '-10', '10L', '-10L', '10.1', '-10.1', u'10',
                       u'-10', u'10L', u'-10L', u'10.1', u'-10.1']
     if not py3compat.PY3:
         _bad_values.extend([long(10), long(-10)])
 
 
 class ComplexTrait(HasTraits):
 
     value = Complex(99.0-99.0j)
 
 class TestComplex(TraitTestBase):
 
     obj = ComplexTrait()
 
     _default_value = 99.0-99.0j
     _good_values   = [10, -10, 10.1, -10.1, 10j, 10+10j, 10-10j,
                       10.1j, 10.1+10.1j, 10.1-10.1j]
     _bad_values    = [u'10L', u'-10L', 'ten', [10], {'ten': 10},(10,), None]
     if not py3compat.PY3:
         _bad_values.extend([long(10), long(-10)])
 
 
 class BytesTrait(HasTraits):
 
     value = Bytes(b'string')
 
 class TestBytes(TraitTestBase):
 
     obj = BytesTrait()
 
     _default_value = b'string'
     _good_values   = [b'10', b'-10', b'10L',
                       b'-10L', b'10.1', b'-10.1', b'string']
     _bad_values    = [10, -10, 10.1, -10.1, 1j, [10],
                       ['ten'],{'ten': 10},(10,), None,  u'string']
     if not py3compat.PY3:
         _bad_values.extend([long(10), long(-10)])
 
 
 class UnicodeTrait(HasTraits):
 
     value = Unicode(u'unicode')
 
 class TestUnicode(TraitTestBase):
 
     obj = UnicodeTrait()
 
     _default_value = u'unicode'
     _good_values   = ['10', '-10', '10L', '-10L', '10.1',
                       '-10.1', '', u'', 'string', u'string', u"€"]
     _bad_values    = [10, -10, 10.1, -10.1, 1j,
                       [10], ['ten'], [u'ten'], {'ten': 10},(10,), None]
     if not py3compat.PY3:
         _bad_values.extend([long(10), long(-10)])
 
 
 class ObjectNameTrait(HasTraits):
     value = ObjectName("abc")
 
 class TestObjectName(TraitTestBase):
     obj = ObjectNameTrait()
 
     _default_value = "abc"
     _good_values = ["a", "gh", "g9", "g_", "_G", u"a345_"]
     _bad_values = [1, "", u"€", "9g", "!", "#abc", "aj@", "a.b", "a()", "a[0]",
                                                         None, object(), object]
     if sys.version_info[0] < 3:
         _bad_values.append(u"þ")
     else:
         _good_values.append(u"þ")  # þ=1 is valid in Python 3 (PEP 3131).
 
 
 class DottedObjectNameTrait(HasTraits):
     value = DottedObjectName("a.b")
 
 class TestDottedObjectName(TraitTestBase):
     obj = DottedObjectNameTrait()
 
     _default_value = "a.b"
     _good_values = ["A", "y.t", "y765.__repr__", "os.path.join", u"os.path.join"]
     _bad_values = [1, u"abc.€", "_.@", ".", ".abc", "abc.", ".abc.", None]
     if sys.version_info[0] < 3:
         _bad_values.append(u"t.þ")
     else:
         _good_values.append(u"t.þ")
 
 
 class TCPAddressTrait(HasTraits):
 
     value = TCPAddress()
 
 class TestTCPAddress(TraitTestBase):
 
     obj = TCPAddressTrait()
 
     _default_value = ('127.0.0.1',0)
     _good_values = [('localhost',0),('192.168.0.1',1000),('www.google.com',80)]
     _bad_values = [(0,0),('localhost',10.0),('localhost',-1), None]
 
 class ListTrait(HasTraits):
 
     value = List(Int)
 
 class TestList(TraitTestBase):
 
     obj = ListTrait()
 
     _default_value = []
     _good_values = [[], [1], list(range(10)), (1,2)]
     _bad_values = [10, [1,'a'], 'a']
     
     def coerce(self, value):
         if value is not None:
             value = list(value)
         return value
 
 class Foo(object):
     pass
 
 class InstanceListTrait(HasTraits):
 
     value = List(Instance(__name__+'.Foo'))
 
 class TestInstanceList(TraitTestBase):
 
     obj = InstanceListTrait()
 
     def test_klass(self):
         """Test that the instance klass is properly assigned."""
         self.assertIs(self.obj.traits()['value']._trait.klass, Foo)
 
     _default_value = []
     _good_values = [[Foo(), Foo(), None], None]
     _bad_values = [['1', 2,], '1', [Foo]]
 
 class LenListTrait(HasTraits):
 
     value = List(Int, [0], minlen=1, maxlen=2)
 
 class TestLenList(TraitTestBase):
 
     obj = LenListTrait()
 
     _default_value = [0]
     _good_values = [[1], [1,2], (1,2)]
     _bad_values = [10, [1,'a'], 'a', [], list(range(3))]
 
     def coerce(self, value):
         if value is not None:
             value = list(value)
         return value
 
 class TupleTrait(HasTraits):
 
     value = Tuple(Int(allow_none=True))
 
 class TestTupleTrait(TraitTestBase):
 
     obj = TupleTrait()
 
     _default_value = None
     _good_values = [(1,), None, (0,), [1], (None,)]
     _bad_values = [10, (1,2), ('a'), ()]
 
     def coerce(self, value):
         if value is not None:
             value = tuple(value)
         return value
 
     def test_invalid_args(self):
         self.assertRaises(TypeError, Tuple, 5)
         self.assertRaises(TypeError, Tuple, default_value='hello')
         t = Tuple(Int, CBytes, default_value=(1,5))
 
 class LooseTupleTrait(HasTraits):
 
     value = Tuple((1,2,3))
 
 class TestLooseTupleTrait(TraitTestBase):
 
     obj = LooseTupleTrait()
 
     _default_value = (1,2,3)
     _good_values = [(1,), None, [1], (0,), tuple(range(5)), tuple('hello'), ('a',5), ()]
     _bad_values = [10, 'hello', {}]
 
     def coerce(self, value):
         if value is not None:
             value = tuple(value)
         return value
 
     def test_invalid_args(self):
         self.assertRaises(TypeError, Tuple, 5)
         self.assertRaises(TypeError, Tuple, default_value='hello')
         t = Tuple(Int, CBytes, default_value=(1,5))
 
 
 class MultiTupleTrait(HasTraits):
 
     value = Tuple(Int, Bytes, default_value=[99,b'bottles'])
 
 class TestMultiTuple(TraitTestBase):
 
     obj = MultiTupleTrait()
 
     _default_value = (99,b'bottles')
     _good_values = [(1,b'a'), (2,b'b')]
     _bad_values = ((),10, b'a', (1,b'a',3), (b'a',1), (1, u'a'))
 
 class CRegExpTrait(HasTraits):
 
     value = CRegExp(r'')
 
 class TestCRegExp(TraitTestBase):
 
     def coerce(self, value):
         return re.compile(value)
 
     obj = CRegExpTrait()
 
     _default_value = re.compile(r'')
     _good_values = [r'\d+', re.compile(r'\d+')]
     _bad_values = ['(', None, ()]
 
 class DictTrait(HasTraits):
     value = Dict()
 
 def test_dict_assignment():
     d = dict()
     c = DictTrait()
     c.value = d
     d['a'] = 5
     nt.assert_equal(d, c.value)
     nt.assert_true(c.value is d)
 
 class TestLink(TestCase):
     def test_connect_same(self):
         """Verify two traitlets of the same type can be linked together using link."""
 
         # Create two simple classes with Int traitlets.
         class A(HasTraits):
             value = Int()
         a = A(value=9)
         b = A(value=8)
 
         # Conenct the two classes.
         c = link((a, 'value'), (b, 'value'))
 
         # Make sure the values are the same at the point of linking.
         self.assertEqual(a.value, b.value)
 
         # Change one of the values to make sure they stay in sync.
         a.value = 5
         self.assertEqual(a.value, b.value)
         b.value = 6
         self.assertEqual(a.value, b.value)
 
     def test_link_different(self):
         """Verify two traitlets of different types can be linked together using link."""
 
         # Create two simple classes with Int traitlets.
         class A(HasTraits):
             value = Int()
         class B(HasTraits):
             count = Int()
         a = A(value=9)
         b = B(count=8)
 
         # Conenct the two classes.
         c = link((a, 'value'), (b, 'count'))
 
         # Make sure the values are the same at the point of linking.
         self.assertEqual(a.value, b.count)
 
         # Change one of the values to make sure they stay in sync.
         a.value = 5
         self.assertEqual(a.value, b.count)
         b.count = 4
         self.assertEqual(a.value, b.count)
 
     def test_unlink(self):
         """Verify two linked traitlets can be unlinked."""
 
         # Create two simple classes with Int traitlets.
         class A(HasTraits):
             value = Int()
         a = A(value=9)
         b = A(value=8)
 
         # Connect the two classes.
         c = link((a, 'value'), (b, 'value'))
         a.value = 4
         c.unlink()
 
         # Change one of the values to make sure they don't stay in sync.
         a.value = 5
         self.assertNotEqual(a.value, b.value)
 
     def test_callbacks(self):
         """Verify two linked traitlets have their callbacks called once."""
 
         # Create two simple classes with Int traitlets.
         class A(HasTraits):
             value = Int()
         class B(HasTraits):
             count = Int()
         a = A(value=9)
         b = B(count=8)
         
         # Register callbacks that count.
         callback_count = []
         def a_callback(name, old, new):
             callback_count.append('a')
         a.on_trait_change(a_callback, 'value')
         def b_callback(name, old, new):
             callback_count.append('b')
         b.on_trait_change(b_callback, 'count')
 
         # Connect the two classes.
         c = link((a, 'value'), (b, 'count'))
 
         # Make sure b's count was set to a's value once.
         self.assertEqual(''.join(callback_count), 'b')
         del callback_count[:]
 
         # Make sure a's value was set to b's count once.
         b.count = 5
         self.assertEqual(''.join(callback_count), 'ba')
         del callback_count[:]
 
         # Make sure b's count was set to a's value once.
         a.value = 4
         self.assertEqual(''.join(callback_count), 'ab')
         del callback_count[:]
 
+class TestDirectionalLink(TestCase):
+    def test_connect_same(self):
+        """Verify two traitlets of the same type can be linked together using directional_link."""
+
+        # Create two simple classes with Int traitlets.
+        class A(HasTraits):
+            value = Int()
+        a = A(value=9)
+        b = A(value=8)
+
+        # Conenct the two classes.
+        c = directional_link((a, 'value'), (b, 'value'))
+
+        # Make sure the values are the same at the point of linking.
+        self.assertEqual(a.value, b.value)
+
+        # Change one the value of the source and check that it synchronizes the target.
+        a.value = 5
+        self.assertEqual(b.value, 5)
+        # Change one the value of the target and check that it has no impact on the source
+        b.value = 6
+        self.assertEqual(a.value, 5)
+
+    def test_link_different(self):
+        """Verify two traitlets of different types can be linked together using link."""
+
+        # Create two simple classes with Int traitlets.
+        class A(HasTraits):
+            value = Int()
+        class B(HasTraits):
+            count = Int()
+        a = A(value=9)
+        b = B(count=8)
+
+        # Conenct the two classes.
+        c = directional_link((a, 'value'), (b, 'count'))
+
+        # Make sure the values are the same at the point of linking.
+        self.assertEqual(a.value, b.count)
+
+        # Change one the value of the source and check that it synchronizes the target.
+        a.value = 5
+        self.assertEqual(b.count, 5)
+        # Change one the value of the target and check that it has no impact on the source
+        b.value = 6
+        self.assertEqual(a.value, 5)
+
+    def test_unlink(self):
+        """Verify two linked traitlets can be unlinked."""
+
+        # Create two simple classes with Int traitlets.
+        class A(HasTraits):
+            value = Int()
+        a = A(value=9)
+        b = A(value=8)
+
+        # Connect the two classes.
+        c = directional_link((a, 'value'), (b, 'value'))
+        a.value = 4
+        c.unlink()
+
+        # Change one of the values to make sure they don't stay in sync.
+        a.value = 5
+        self.assertNotEqual(a.value, b.value)
+
 class Pickleable(HasTraits):
     i = Int()
     j = Int()
     
     def _i_default(self):
         return 1
     
     def _i_changed(self, name, old, new):
         self.j = new
 
 def test_pickle_hastraits():
     c = Pickleable()
     for protocol in range(pickle.HIGHEST_PROTOCOL + 1):
         p = pickle.dumps(c, protocol)
         c2 = pickle.loads(p)
         nt.assert_equal(c2.i, c.i)
         nt.assert_equal(c2.j, c.j)
 
     c.i = 5
     for protocol in range(pickle.HIGHEST_PROTOCOL + 1):
         p = pickle.dumps(c, protocol)
         c2 = pickle.loads(p)
         nt.assert_equal(c2.i, c.i)
         nt.assert_equal(c2.j, c.j)
 
 class TestEventful(TestCase):
 
     def test_list(self):
         """Does the EventfulList work?"""
         event_cache = []
 
         class A(HasTraits):
             x = EventfulList([c for c in 'abc'])
         a = A()
         a.x.on_events(lambda i, x: event_cache.append('insert'), \
             lambda i, x: event_cache.append('set'), \
             lambda i: event_cache.append('del'), \
             lambda: event_cache.append('reverse'), \
             lambda *p, **k: event_cache.append('sort'))
 
         a.x.remove('c')
         # ab
         a.x.insert(0, 'z')
         # zab
         del a.x[1]
         # zb
         a.x.reverse()
         # bz 
         a.x[1] = 'o'
         # bo
         a.x.append('a')
         # boa
         a.x.sort()
         # abo
 
         # Were the correct events captured?
         self.assertEqual(event_cache, ['del', 'insert', 'del', 'reverse', 'set', 'set', 'sort'])
 
         # Is the output correct?
         self.assertEqual(a.x, [c for c in 'abo'])
 
     def test_dict(self):
         """Does the EventfulDict work?"""
         event_cache = []
 
         class A(HasTraits):
             x = EventfulDict({c: c for c in 'abc'})
         a = A()
         a.x.on_events(lambda k, v: event_cache.append('add'), \
             lambda k, v: event_cache.append('set'), \
             lambda k: event_cache.append('del'))
 
         del a.x['c']
         # ab
         a.x['z'] = 1
         # abz
         a.x['z'] = 'z'
         # abz
         a.x.pop('a')
         # bz 
 
         # Were the correct events captured?
         self.assertEqual(event_cache, ['del', 'add', 'set', 'del'])
 
         # Is the output correct?
         self.assertEqual(a.x, {c: c for c in 'bz'})