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Our tests around the ticket update listener are looking pretty good but both the tests we have right

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now are really happy Pap tests there assume that everything is working as expected.

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I'd really like to add in at least one test to make sure that we can handle kind of bad scenarios as

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well.

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Let me show you a diagram and explain what I would like to test.

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Back to the side gram.

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We've looked at it many times.

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We're going to assume that inside of our orders database we've got a ticket with an idea Susie Q and

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A version of 1 Well then imagine that these two events right here get emitted and now maybe for whatever

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reason we accidentally process this second update event first.

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That is not what we would want.

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We would want to always process this event with the version to first but as we've seen it is entirely

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possible that we will accidentally process these things out of order.

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So in this scenario we've got a version of three on the incoming event but we still have only version

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1 inside of our database and so it's very clear that we are missing the event with version 2.

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So in this scenario we would want to either throw an error or at the very least make sure that we do

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not call the ACH function.

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Remember if we call the act function that means we are acknowledging the message and we are telling

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that string server that this event has been processed.

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If we just don't call the act function then that streaming server is going to try to emit this event

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again.

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Five seconds in the future and hopefully in that window we will have enough time to process the version

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to even that's it.

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That's all we're going to test.

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We're going to once again create an instance of our listener.

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We're going to create our data event and we're going to give it a version kind of far into the future

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and then just make sure that either we throw an error or at the very least that we do not call the ACH

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function.

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All right.

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So back inside my editor I'm gonna go down to the very bottom and I'll say it does not call EQ if the

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event is in the future.

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Or how about if the event has a future version.

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Or how about has a skipped version number or something like that.

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I'm sure you could think of a better description the one I've got good enough.

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I'll make sure I marked this function as a sink and inside of here we'll get message data listener.

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I don't think we need the ticket but let's get it anyways we might need it now we need to somehow make

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sure that our data object has a version that is far into the future so a future version we can do so

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very easily by just taking a look at the version property on there and sending it to some future version

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number.

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I'll just say data dot version equal to 10.

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That's definitely very far in the future and certainly there are some missing version events between

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the one that our ticket has or the current tickets version and this version of 10 right here.

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So now we will call our listener on message with that data object and message so when we run this now

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we should end up.

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If we go back over to the listener itself you're sick.

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Update listener when we run this query we should not be finding a ticket at all.

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We should enter this if statement and end up throwing in air and so we want to make sure that we somehow

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capture that air inside of our tests as we don't want to actually throw it inside the test itself.

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We need to capture that thing and then hopefully also write out some kind of expectation that says that

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the message not at function does not get called to do so.

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I'm going to wrap this thing with a try catch statement

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in this case.

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We're not really gonna do anything inside of the catch we're just using that catch to make sure that

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we do not throw an air out of this entire test which would automatically cause the entire thing to fail.

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Then right after the try catch statement we can put in an expectation we're going to expect message

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not ask not to have been called.

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That's our goal here.

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We want to make sure that we did not call that act function.

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Let's say this and see how we're doing back over at the terminal and it looks like our update listener

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tests are still passing as usual.

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Let's try to make this thing fail.

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Just make sure that the test is really working as expected.

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So how about in this scenario.

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Let's try changing about the data version right here.

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Let's just come at that out.

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So now we should have some accurate or correct version and we should be calling the ACT function.

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They'll say that pull it back over

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and there we go.

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So we got an error here because the act function was actually called well so oncoming that and I think

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we're good to go all right.

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So I think that's a good series of tests around our on message function.

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Let's take a pause right here.

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And as usual continue in just a moment.