def test_connect_same_trait_target_undefined(self, A=_B, B=_A):
"""Verify two traitlets of the same type can be linked together using link."""
a = A(value=9)
b = B() # b.value is Undefined
# Conenct the two classes.
c = link((a, 'value'), (b, 'value'))
assert b.value == 9
# Change one of the values to make sure they stay in sync.
a.value = 5
assert a.value == b.value
b.value = 6
assert a.value == b.value
del b.value # Reset trait (to Undefined in this case)
if has_traitlets(a):
# linking sets b.value to 0 if it has traitlets
assert a.value == 0
else:
assert a.value is t.Undefined
def test_connect_same_trait_source_undefined(self, A=_A, B=_B):
"""Verify two traitlets of the same type can be linked together using link."""
a = A() # a.value is Undefined
b = B(value=8)
# Conenct the two classes.
c = link((a, 'value'), (b, 'value'))
# Linking doesn't change b.value because a.value is undefined
assert b.value == 8
# Change one of the values to make sure they stay in sync.
a.value = 5
assert a.value == b.value
b.value = 6
assert a.value == b.value
del a.value # Reset trait (to Undefined in this case)
if has_traitlets(b):
# linking sets b.value to 0 if it has traitlets
assert b.value == 0
else:
assert b.value is t.Undefined