[Telepathy] twisted test question

[Alban Crequy]

Le Tue, 27 Jan 2009 15:29:21 -0600,
Jonathon Jongsma <jonathon.jongsma at collabora.co.uk> a écrit :

> As many of you are aware, I'm adding some test cases to
> telepathy-idle.  I have a decent feel for the test infrastructure
> now, but I don't see any way to assert that an event doesn't happen.
> For instance, if you want to assert that a dbus-signal is emitted,
> you can do things like:
> 
> 	q.expect('dbus-signal', ...)
> 
> but I don't see any way to specify that something shout NOT happen,
> maybe something like:
> 
> 	q.expect_not('dbus-signal', ...)
> 
> or perhaps more usefully, something like:
> 
> 	q.expect_many(EventPattern('foo'),
>          	      EventPattern('bar'),
> 	              ForbidEventPattern('baz'))
> 
> that would require events 'foo' and 'bar' to happen but fail if event
> 'baz' occurs.
> 
> Is there anything like that available?  Has anybody wanted to do
> something similar and found a different way to achieve it?

You can have a look here:
http://git.collabora.co.uk/?p=telepathy-gabble.git;a=blob;f=tests/twisted/test-caps-hash.py;h=17280f4fd35c6d18c5184deacec81f2a2236afa5;hb=master#l335

You can register a callback when the dbus-signal is fired, and set up a
flag in the callback.

def caps_changed_cb(dummy):
    # Workaround to bug 9980: do not raise an error but use a flag
    # https://bugs.freedesktop.org/show_bug.cgi?id=9980
    global caps_changed_flag
    caps_changed_flag = True

conn_caps_iface.connect_to_signal('CapabilitiesChanged',
caps_changed_cb)

Then you can assert your flag is False.

global caps_changed_flag
# don't receive any D-Bus signal
sync_dbus(bus, q, conn)
assert caps_changed_flag == False

It is not as easy as q.expect_not because you need some synchronisation
(sync_dbus...), and you cannot assert directly in the callback because
of bug #9980.

I am not sure 'ForbidEventPattern' is easy to write because you
would need to synchronise on possible events (D-Bus, streams).

-- 
Alban