jsverify VS redux

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.

Redux

redux - Redux is a key tool used in managing state across an application. This can be used with any web technology including React, Vue and Angular docs

Redux is a client-state library.

react-redux: A powerhouse for efficient state management and data flow control. Learn more

Reducer-based: requires dispatching actions to update a big centralised state, often called a “single source of truth”. In this group, we have Redux and Zustand.

I am _thrilled_ to announce that:

Redux Toolkit 2.0 is LIVE!!!

- https://github.com/reduxjs/redux-toolkit/releases/tag/v2.0.0

This major version has new features, faster perf, smaller bundle size, and removes deprecated options.

It's accompanied by majors for all our Redux family packages

## RTK 2.0:

- a new `combineSlices` method for lazy-loading reducers - Updates to `createSlice` to include a `selectors` field and allow defining thunks inside

- Immer 10 w/ faster updates

- Removal of deprecated options

See the migration guide:

- https://redux.js.org/usage/migrations/migrating-rtk-2

All of the Redux libraries now have modernized packaging with full ESM/CJS compat. They also ship modern JS (no transpiling for IE11), which means smaller bundle sizes.

We've also done byte-shaving work to shrink the bundles (extracting error messages, de-duping imports)

## Redux core 5.0:

- The TS conversion we did in 2019!

- Action types _must_ be strings

- `UnknownAction` as the default action type

- Better preloaded state types

- Internal subscription improvements

- Still marks `createStore` as deprecated!

- https://github.com/reduxjs/redux/releases/tag/v5.0.0

## React-Redux 9.0:

- *Now requires React 18 and RTK 2.0 / Redux 5.0*

DEV is a Rails monolith, which uses Preact in the front-end using islands architecture. The reason why I mention all this is that it's not a full-stack JavaScript application, and there is no state management library like Redux or Zustand in use. The data store, for the most part on the front end, is all data attributes.

Oh hey, that's my post!

(yes I spend too much time refreshing HN :) )

FWIW I did end up with a packaging combination that seems to work sufficiently. I never did fix the "FalseCJS" issue that `are-the-types-wrong` is detecting. I played with double-emitting TS typedefs, and the `tsup` tool _does_ actually have support for that now (added by Andrew Branch from the TS team). So it might be more feasible now. But ultimately I decided I was tired of messing with packaging setup and that what I've got is good enough. (hopefully)

We're actually about to launch Redux Toolkit 2.0 and Redux 5.0 this week, assuming the last couple pieces come together. Here's the latest RCs - you can see the current `package.json` files in there:

- https://github.com/reduxjs/redux-toolkit/releases/tag/v2.0.0...

- https://github.com/reduxjs/redux/releases/tag/v5.0.0-rc.1