Define commands on-the-fly without creating a class

[moodmosaic]

The following interface should be implemented (by a class) in order to define a synchronous command:

interface Command<Model extends object, Real>

In addition to that, can a command be defined as a pair (or actually a triple) that holds the functions check, run, toString? Just trying to figure out if I can define commands without classes at all.

(Or, perhaps TypeScript has something similar to F# Object Expressions where you can implement an interface on-the-fly, without having to create a class.)

[dubzzz]

I think the on-the-fly should work fine with https://github.com/dubzzz/fast-check/blob/main/packages/fast-check/src/arbitrary/commands.ts#L40. The interface is mostly there to give the typing related contraints but not for extends needs (at least for the ICommand and derived stuffs).

[dubzzz]

But you'll probably need to setup of the fields requested by the contract.

[nth-commit]

Can confirm, I use commands without a class:

type Command = fc.AsyncCommand<Model, Real>

const createCommand = (): Command => ({
  check: (m) => true,
  // ... etc.
})

[moodmosaic]

Awesome, thank you Michael.

[moodmosaic]

Sidenote: Great work on GalaxyCheck! I like the idea of Sample as an attribute, among other stuff 🚀 (Also, greetings from the core Hedgehog team 🦔)

[nth-commit]

Thanks @moodmosaic! I definitely know who you are (we might have even interacted in the Hedgehog issues a long time ago), and I think Hedgehog is really great.

I need to go and brush up the docs and release a stable version. I thought having a C# day job again would bring me closer to it, but turns out that writing C# all day is more than enough C# 😅

[nth-commit]

Here's some examples if it helps:

I'm using a bespoke wrapper around the creating commands which lets me check some invariants after each command, have a default the check function, etc: https://github.com/nth-commit/xfiat/blob/620566179cf64cd3ab8b409145f838916804f49b/test/helpers/AsyncCommandFactory.ts

This is where I'm using that helper to specify some commands: https://github.com/nth-commit/xfiat/blob/620566179cf64cd3ab8b409145f838916804f49b/test/ReserveFunding/LiquidityAccumulatingModel.ts#L61-L101

And here is where I'm specifying my invariants: https://github.com/nth-commit/xfiat/blob/620566179cf64cd3ab8b409145f838916804f49b/test/ReserveFunding/LiquidityAccumulatingModel.ts#L31-L47