jsverify VS proposal-pipeline-operator

Libraries like JSVerify or Fast-Check offer essential tools to facilitate property-based testing.

I tend to use anything that offers property-testing, since tests are much shorter to write and uncover lots more hidden assumptions.

My go-to choices per language are:

- Python: Hypothesis https://hypothesis.readthedocs.io/en/latest (also compatible with PyTest)

- Scala: ScalaCheck https://scalacheck.org (also compatible with ScalaTest)

- Javascript/Typescript: JSVerify https://jsverify.github.io

- Haskell: LazySmallCheck2012 https://github.com/UoYCS-plasma/LazySmallCheck2012/blob/mast...

- When I wrote PHP (over a decade ago) there was no decent property-based test framework, so I cobbled one together https://github.com/Warbo/php-easycheck

All of the above use the same basic setup: tests can make universally-quantified statements (e.g. "for all (x: Int), foo(x) == foo(foo(x))"), then the framework checks that statement for a bunch of different inputs.

Most property-checking frameworks generate data randomly (with more or less sophistication). The Haskell ecosystem is more interesting:

- QuickCheck was one of the first property-testing frameworks, using random genrators.

- SmallCheck came later, which enumerates data instead (e.g. testing a Float might use 0, 1, -1, 2, -2, 0.5, -0.5, etc.). That's cute, but QuickCheck tends to exercise more code paths with each input.

- LazySmallCheck builds up test data on-demand, using Haskell's pervasive laziness. Tests are run with an error as input: if they pass, we're done; if they fail, we're done; if they trigger the error, they're run again with slightly more-defined inputs. For example, if the input is supposed to be a list, we try again with the two forms of list: empty and "cons" (the arguments to cons are both errors, to begin with). This exercises even more code paths for each input.

- LazySmallCheck2012 is a more versatile "update" to LazySmallCheck; in particular, it's able to generate functions.

The usage of hypothesis is very intuitive and simple, and presents the concept of property-based testing perfectly. So I also wanted to find an equivalent alternative in Node. Two of them have high star ratings on Github, JSVerify with 1.6K stars and fast-check with 2.8K stars. So I took some time to study fast-check a little bit and try to get closer to my daily work.

Systems I've used for this include https://agda.readthedocs.io/en/v2.6.0.1/getting-started/what... https://coq.inria.fr https://www.idris-lang.org and https://isabelle.in.tum.de

An easier alternative is to try disproving the statement, by executing it on thousands of examples and seeing if any fail. That gives us less confidence than a full proof, but can still be better than traditional "there exists" tests. This is called property checking or property-based testing. Systems I've used for this include https://hypothesis.works https://hackage.haskell.org/package/QuickCheck https://scalacheck.org and https://jsverify.github.io

Using create-react-app, you’ll run npm test which uses Jest internally. If you are dealing with a lot of data on the UI, or using TypeScript, use JSVerify for property tests. For end to end tests, Cypress is a great choice.

Current Status: You'd have to check the TC39 proposals repository or the official proposal text for the most recent status. As of my last update, it had not yet reached Stage 4 (final stage) of the TC39 process, which means it wasn't part of the ECMAScript specification yet.

Javascript may get it https://github.com/tc39/proposal-pipeline-operator https://youtu.be/dQw4w9WgXcQ

It can be further simplified. For example, you don't need two separate functions to extract the first chat completion message etc.

This version:

- uses existing language constructs

- can be immediately understood even by the most junior devs

- is likely to be 1000 times faster

- does not rely on an external dependency that currently has 143 issues and every two weeks releases a new version adding dozens of new methods to things

Note: one thing I do wish Javascript adopted is pipes: https://github.com/tc39/proposal-pipeline-operator

Still in stage 2 atm https://github.com/tc39/proposal-pipeline-operator

Both are active tc39 proposals :)

https://github.com/tc39/proposal-pipeline-operator - Stage 2

https://github.com/tc39/proposal-pattern-matching - Stage 1

Hopefully we get both in the next couple of years.

Some time ago I saw how hyped JS community was about pipeline operator proposal. So I tried to make something similar in python. There is how tipe module was created. Check it out if you are interested: https://github.com/mishankov/tipe

We often add promising TC39 proposals into Civet so people can experiment without waiting.

We've added https://github.com/tc39/proposal-pipeline-operator, a variant of https://github.com/tc39/proposal-pattern-matching, a variant of https://github.com/tc39/proposal-string-dedent and others.

Since our goal is to be 99% compatible with ES we'll need to accommodate any proposals that become standard and pick up anything TC39 leaves on the table (rest parameters in any position, etc.)

The Proposal is for the Hack pipe, so your example would be