Method test_callbacks

tests/test_traitlets.py:2097–2138

Verify two linked traitlets have their callbacks called once.

(self)

        self.assertEqual(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[:]

    def test_tranform(self):
        """Test transform link."""