Add a getting started tutorial

[dubzzz]

Content:

• explain property based
• example sort: from project setup to properties

[bitjson]

This would be very helpful. 💯

Particularly, I'd really appreciate a succinct example for the more QuickCheck-like use case, where you're exercising functionality in lots of random orders to find strange issues. I have a todo test here which I'd love to know the most idiomatic way to accomplish with fast-check.

I already did some simple "input -> result" fast-check assertions in that file (to ensure compatibility with other implementations of secp256k1), but I actually only found this bug in manual testing.

Returned Typed Arrays were using references to internal buffers rather than copies of them, so if you used library methods in a certain order, and continued trying to use earlier results, your earlier results were continuing to be modified by the library (since I was accidentally giving you a reference rather than a copy). I'd love to see an example which uses fast check to try all the various different methods in many orders, and confirm that we still get reasonable results.

[dubzzz]

Partial answer for the moment, I need to dig a little bit more in your message before coming with a full answer.

Concerning:

I'd love to see an example which uses fast check to try all the various different methods in many orders, and confirm that we still get reasonable results.

I have an opened issue #8 to implement commands-like approach - model based testing. I have seen this method in used with RapidCheck C++.

Snippet example (C++ code): https://github.com/emil-e/rapidcheck/blob/master/examples/counter/main.cpp
More details at: https://labs.spotify.com/2015/06/25/rapid-check/

Basically you define commands with:

• preconditions
• run

And your done ;) The framework does all the magic for you.

It is really a feature I want to see in fast-check, so I will definitely work on it whenever I got enough time to think of a nice implementation. I want to apply this approach for UI testing (I already built a POC for that at work based on fast-check).

[dubzzz]

@bitjson I just submitted an example of simple implementation of model based testing based on fast-check. See Model based testing example #120

For the moment, I do not provide a built-in implementation in the framework. It would require some more work:

• fc.array is not suitable for a quick shrink on commands - we can truncate the array right after the first failure
• need to deal with asynchronous code for real implementation and maybe for model - still doing experiments to check if it is needed on model side

Related to your point:

I'd love to see an example which uses fast check to try all the various different methods in many orders, and confirm that we still get reasonable results.

[dubzzz]

In reality, given #120, there is very few work to do to have a ready to use solution. If it solves your problem I can start adding this feature to fast-check in a next minor.

Basically, I can:

• start by taking this code
• keep using fc.array for the moment
• add an async implementation for the executor

And this is it.

[dubzzz]

@bitjson Just added a hands-on tutorial containing both a definition of property based and a sample project example tested with fast-check. Available directly from the README

[bitjson]

@dubzzz awesome! Thanks for the examples, those are both very helpful.

And I would love to be your first user for a built-in model based testing framework! Just let me know when you have something ready for me to try – I'll try it on the Secp256k1 interface in bitcoin-ts.

[dubzzz]

Closing the issue. There is an open issue to keep track on the model based way