[Haskell-cafe] quickcheck for compiler testing

[Paul Brauner]

There's a recent paper by Jonas Duregård et al where they introduce a
variant of feat that allows for efficient discarding of unwanted values, à
la lazy Smallcheck. The motivating example of the paper is exactly what
you're looking for: discarding ill-formed programs.

On Mon, Feb 16, 2015, 19:44 Andrey Chudnov <achudnov at gmail.com> wrote:

>  If you just need an example for generating and shrinking arbitrary ASTs,
> you can have a look here:
> https://github.com/jswebtools/language-ecmascript/blob/master/src/Language/ECMAScript3/Syntax/Arbitrary.hs
> . Note that I use the testing-feat package to generate Gen instances --- it
> tends to do better (explore interesting cases earlier) than handwritten
> code --- and then fix-up incorrect ASTs (another option is to simply
> discard them).
>
>
> On 02/16/2015 12:33 PM, Maurizio Vitale wrote:
>
> By 'test size reduction' I mean the 'shrink' function. It seems to me (as
> I said, first Haskell program and no experience with quickcheck) that it
> works nicely with a topdown generation of the test, but I don't see how to
> easily generate correct programs that way.
>
>  Even if you cannot release your tests, maybe you can help me with a very
> simple case. Consider a trivial AST. A program is a possibly nested block.
> Each block is a bunch of declarations of variables and some use of them
>
>   data Block = Block [Declaration] [Statement]
>
>   data Declaration = Var String String
>
>   data Statement = Statement Block | Use String
>
>
>  How one would generate things like:
>
>  Block [Var "a" "int"] [Use "a"] -- here a is declared in the same block
>
>  Block [] [Statement Block [Var "s" "int"] [Statement Block [] [Use
> "s"]]] -- here s is declared in some other visible scope
>
>
>  etc.
>
>  Or am I trying to approach the problem from the wrong angle?
>
>
>
> On Mon, Feb 16, 2015 at 12:02 PM, Andrey Chudnov <achudnov at gmail.com>
> wrote:
>
>>  I use QuichCheck for compiler testing where I generate random, but
>> well-formed programs and check some high-level syntactic properties on
>> results. The QuickCheck instance is open-source (see language-ecmascript),
>> but the compiler-test code is closed-source at this time. Still, I found
>> that it's not the ultimate answer: many properties are hard to formalize,
>> so I have to resort to unit tests. I'm not sure what you mean by "how this
>> would play with test size reduction". I think it's worth giving a try, but
>> keep in mind that you might still need to use unit tests.
>>
>> Let me know if you have any questions.
>>
>> /Andrey
>>
>>
>> On 02/16/2015 11:53 AM, Maurizio Vitale wrote:
>>
>>  I'm starting to work on my first real haskell program (I've only RWH
>> exercises under my belt) and wondering whether people use quickcheck at all
>> for compiler testing.
>>
>>  I've seen uses of quickcheck for testing parsers, but I'm interested in
>> generating well-formed programs (e.g. random programs with all declarations
>> in reasonable random places). This could be used to test passes other than
>> parsing (or even parsing, for languages that needs to distinguish
>> identifiers, like the 'typedef' problem in C/C++).
>>
>>  The only thing I can think of, is to use quickcheck for randomly
>> generating statements, go over them and figure out free variables (incl.
>> functions) and generate declarations in random places for them. But I'm not
>> sure how this would play with test size reduction and doesn't look like a
>> nice solution anyhow.
>>
>>  Any idea or pointers to examples? or should I give up on quickcheck for
>> this and just do direct testing?
>>
>>  Thanks,
>>
>>    Maurizio
>>
>>
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