Ayende @ Rahien

My name is Oren Eini
Founder of Hibernating Rhinos LTD and RavenDB.
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Create a test DSL to test the DSL

time to read 1 min | 87 words

Yesterday I asked how we can efficiently test this piece of code:

specification @vacations:
	requires @scheduling_work
	requires @external_connections

Trying to test that with C# code resulted in 1500% disparity in number of lines of code. Obviously a different approach was needed. Since I am in a DSL state of mind, I wrote a test DSL for this:

script "quotes/simple.boo"

with @vacations:
	should_require @scheduling_work
	should_require @external_connections	

with @scheduling_work:

I like this.

You can take a look at the code here.


James Gregory

Nice, but how are you going to test that the testing DSL works? ;)


Are you going to test this new DSL with itself?

Ayende Rahien

Quis custodiet ipsos custodes?

Benny Thomas

Its kind of nice. You have to write a TestDSL engine to test your dependencies on your DSL script.

What happens if you shuffle the should_require statements?

Ayende Rahien

Nothing much, there isn't an order dependency in the implementation that I wrote for them

Aaron Jensen

That's a lot more than a 1500% disparity now (yes I know it's just framework code and its not repeated, I'm just being pedantic). I think writing another full on boo dsl for testing something so trivial is a bit extreme. Why not just a base test class? Or some extension methods?




Totally breaks AAA, but that's easily fixable.


Creating testing DSL's is something I just started doing and it has been awesome. I found that there are certain patterns that one tests repeatedly, so this can help.


You aren't testing the code, you're writing the same program twice :-)

Is this really useful?

Ayende Rahien


Try this, then:


specification @vacations:

requires @scheduling_work

requires @external_connections if UserCount > 50


with @vacations, Users(51):

should_require @scheduling_work

should_require @external_connections

with @vacations, Users(49):

should_require @scheduling_work

should_not_require @external_connections
Ayende Rahien


That is because you consider only the code that you have here. Consider the case of a useful DSL where you have plenty of scripts that you want to test.

Since the cost of writing a DSL is very low, I see this is as a huge benefit.


yes. that also. 1500% is exactly... well... more or less more than 90% less time.

i like this too.

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