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
Do you see my problem more clearly with this example? Or have I
obfuscated it even more... :)
cr
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