Recommended way to display/debug arbitraries?

[Stuart Hungerford]

Sometimes it's handy to see the kinds of values the various Arbitrary functions are generating. This could be for debugging purposes, simple curiosity or even using the generated values in a non-testing context.

I can see a few of ways of doing this:

1. Add a Console.log temporarily into any function under test.

2. Create a FastCheck.Property.Sync.assertPropertyn called Displayn that always returns true and contains a Console.log etc.

3. Some kind of Arbitrary combinator that flattens the generated values into a "plain" array.

Is there a more fast-check idiomatic way of doing this?

[Andrew Herron]

Sorry for not getting to this over the weekend. This isn't something I have dealt with all that much, I might verify that I'm generating the values correctly but that's separate to running fast-check on them; at that point I trust it to give me the smallest replication case possible.

As for your request, I try to avoid having code in this library that is emitted when compiled. It is what we call "zero cost"; this gives me less to maintain when fast-check changes. The big exception to this is the assertProperty wrapper functions which are mostly there because I learned property testing with JsVerify and it offered something similar.

I suggest asking in the fast-check repo, or maybe checking the fast-check docs. If there is a feature to assist with this that I haven't made a binding for, I'm certainly happy to add one.

[Stuart Hungerford]

Thanks -- that all makes sense. I also discovered the fast-check sample function which is useful for separate studies of the arbitrary values being produced.