On 27 Aug 2009, at 17:02, Chuck Remes wrote:
On Aug 27, 2009, at 10:12 AM, Matt Wynne wrote:
On 26 Aug 2009, at 19:57, Chuck Remes wrote:
I'm trying to setup some specs (really just assertions) that
verify some callbacks are executed in response to COM events. In
the WIN32OLE_EVENT class you may subscribe to a COM event and have
it delivered to you for processing. Syntax looks like:
event_handler.on_event('StartEvent') do |*args|
do_start_event args
end
The #do_start_event method is a member of the containing class.
The only way I can confirm that it is being called is to set an
expectation on the class under test. I've always noted that
mocking/stubbing the class under test is rather bad form.
Regardless, I don't know how to "mock" the delivery of an event
anyway so this may all be moot.
I searched the list archives for 'win32ole' back to early 2007 and
came up with 0 hits. Any suggestions on how to tackle this?
This doesn't really have much to do with the specific technology
you're dealing with, it's an issue about separating the layers so
you can introduce fakes where you need to in order to test your own
code.
Can you use dependency injection (or some other trick) to swap in a
fake event_handler into the code you've quoted above? If so, you
can then get your fake to simulate the behaviour of the
event_handler and exercise the code you want to actually test.
There are a couple of good books on these sort of techniques:
http://xunitpatterns.com/
http://www.amazon.com/Working-Effectively-Legacy-Michael-Feathers/dp/0131177052
does that help?
It does somewhat. I will definitely be looking at that XUnit
patterns book.
To answer an earlier question, I *can* pass in a mock for
event_handler. However, I fail to see how I can use that in the
example above to test that the statements in the block are executed.
def bar event_handler
event_handler.on_event('StartEvent') do |baz, qux|
@obj1.method1 baz, qux
end
end
Let's assume that method1 and method2 are acting upon other objects
that I can also mock via DI. How can I generate the 'StartEvent' so
that the block above is executed? BTW, the layers are as separated
as they are going to get. In the WIN32OLE_EVENT class you *must*
pass a block as shown above. I don't know how to get that block to
execute in my specs without actually connecting to the COM service
and getting it to generate that 'StartEvent'. Do you know of another
way?
it "should execute the block upon receipt of event 'StartEvent'" do
handler = mock("event handler")
handler.should_receive(:on_event).with('StartEvent') # necessary?
obj1_mock = mock("obj1")
obj1.should_receive(:method1)
foo = Foo.new
foo.obj1 = obj1
foo.bar
# callback has been set; how do I generate the 'StartEvent'
# to run that block?
foo.???
end
So I'm not sure if you can simulate a block being yeilded with RSpec's
mocks, it's probably possible but I think you'd be simpler using a
hand-made fake:
class FakeEventHandler
def initialize(*args_to_yield)
@args_to_yield = *args_to_yield
end
def on_event(event_name)
yield *...@args_to_yield
end
end
Something like that.
Point being, a test-double (fake) doesn't always have to be a mock
object.
_______________________________________________
rspec-users mailing list
[email protected]
http://rubyforge.org/mailman/listinfo/rspec-users
