class FakeEmailSender(list):

    def send(self, address: str, message: str) -> None:
        self.append((address, message))


def test_when_a_customer_signs_up():

    sender = FakeEmailSender()
    handler = SignupHandler(sender)

    handler("[email protected]", "password")

    assert (("[email protected]", "welcome to the website")) in sender

from spyfi import Spy


class Thing:

    def __init__(self, colour):
        self.colour = colour

    def say_hello(self, message):
        print(f"Hello, I am a {self.colour} thing: {message})


class ThingFactory:

    def make_thing(self, colour:str) -> Thing:
        return Thing(colour)


def test_thing_messages():

    # Spiffy takes any old object and wraps its methods
    # so that an arbitrary callback receives args and kwargs.
    # In this case, we're appending all calls to a list.
    spy = Spy(ThingFactory())

    # The returned object is otherwise unchanged. `factory` is a real
    # ThingFactory and behaves as normal.
    factory = spy.target
    factory.make_thing("blue").say_hello("I like python")

    # Since we have access to the calls list, we can assert that
    # particular methods were called with the right data.
    assert len(spy.calls) == 2
    assert calls[0].method == "make_thing"
    assert calls[0].args == ("blue",)

    # Spyfi includes a helper method to make assertions easier
    assert spy.has("say_hello")
    assert spy.has("say_hello", "I like python")