Re: [Haskell-cafe] ANN: leancheck-v0.7.4 with providers for Tasty, Hspec and test-framework
Hi. I do prefer the enumerative approach for test case generation over the randomized one (quickcheck) because I have use cases (testing student code) where I want to avoid IO, and I just want a pure list of (small) counterexamples. Among the enumerative testing libraries, the "competition" is between leancheck and smallcheck. For, me the important differences are Enumeration of algebraic data types (ADTs), via built-in serial combinators, e.g., cons0 Leaf \/ cons2 Branch * leancheck enumerate by size (number of nodes in tree) * smallcheck enumerates by depth (longest path in tree) I (much!) prefer "by size" because this delays combinatorial explosion somewhat. Automated Listable/Serial instances for ADTs * leancheck uses template-haskell * smallcheck uses DeriveGeneric Here I would actually prefer DeriveGeneric. But this certainly could be added to leancheck? Oh, and leancheck does not use fancy typeclassery (smallcheck needs Multiparamtypeclasses and Monads just to declare a Serial instance) and it is also easier to get at the list of counterexamples. - J.W.
Hi, I'm glad you liked LeanCheck. :-) On Mon, 10 Sep 2018 15:09:43 +0200, Johannes Waldmann wrote:
Among the enumerative testing libraries, the "competition" is between leancheck and smallcheck. For, me the important differences are
Enumeration of algebraic data types (ADTs), via built-in serial combinators, e.g., cons0 Leaf \/ cons2 Branch
* leancheck enumerate by size (number of nodes in tree) * smallcheck enumerates by depth (longest path in tree)
I (much!) prefer "by size" because this delays combinatorial explosion somewhat.
Yes, size bounded enumeration is more tractable. The combinatorial explosion is still there, but a lot of the times much later in the enumeration. LeanCheck also avoids repeating tests. SmallCheck may/will repeat tests when testing successive "depths".
Automated Listable/Serial instances for ADTs
* leancheck uses template-haskell * smallcheck uses DeriveGeneric
Here I would actually prefer DeriveGeneric.
Might I ask why the preference?
But this certainly could be added to leancheck?
Yes it could. I guess LeanCheck could provide a genericTiers / defaultTiers function (of type something like `Generic a => [[a]]`) on an optional module so that one would write: import Test.LeanCheck.Generic instance Listable MyType where tiers = genericTiers Patches or GitHub pull requests are always welcome. :-) -- I may add this myself if I ever get the time. Another addition could be defining a "default" inside the Listable typeclass itself so that one could write `data MyType = ... deriving Listable`. But I'm not very keen on this second option, as it would require an extension on LeanCheck's core which is compliant with Haskell98+Namespaces. It would also hinder the beginner-friendliness of reading that module. (Or maybe there is a way to define "orphan" default declarations for typeclasses in separate modules?)
Oh, and leancheck does not use fancy typeclassery (smallcheck needs Multiparamtypeclasses and Monads just to declare a Serial instance) and it is also easier to get at the list of counterexamples.
This was intentional, I'm a fan of simple types and interfaces. I'm glad you liked this. - Rudy
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Rudy Matela -
waldmann