Automated reasoning for React/ReasonML
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Welcome to VerifiedReact! This is work in progress - stay in touch via @VerifiedByAI, or come chat with us on Discord.

For an overview, read our Medium post Introducing Verified React.

Verified React logo

Ideas, aims and progress so far

  • Stage 1 (Counter, TicTacToe)

    • Simpler automation of Imandra:
      • added imandra-http-server as an alternative to imandra-repl to allow automation via an HTTP api, bundled with the Imandra installer. Previously you could automate our imandra-repl process via stdin/stdout, but having an HTTP interface to the Imandra client naturally makes life a lot easier. imandra-http-server is built using our Imandra_client OCaml library, which we're hoping to make available as an opam package in the future, so OCaml users can use the Imandra client directly from their code.
      • added bs-imandra-client - bucklescript bindings to that HTTP api to be used when running on Node
    • Allow export of export of core logic verified with Imandra to code that can be compiled to executable JS
      • Imandra comes with a prelude of pre-verified functions for use from .iml (Imandra-ml) or .ire (Imandra-reason) code. When you're done reasoning and want to compile the verified module into a larger program, you need a .ml version of the prelude to compile alongside your module. Previously this was available to compile as native OCaml package, but we've now also included an initial amended version that compiles to javascript via the bucklescript compiler too, which can be npm installed from the imandra-prelude repo.
    • Automation of verification goals via jest, via imandra-http-server. See:
      • examples/simple/__tests__/
      • examples/tictactoe/__tests__/
      • examples/todomvc/__tests__/
    • Hook verified state machine up to React reducer component. See:
      • examples/tictactoe/
  • Stage 2

  • Stage 3

    • Collecting React reducer events from React unit test runs
    • Map reducer events back to state machine events, and visualise coverage on the decomposition
    • Coverage report of state space as hit by your jest tests


Make sure you have the latest version of imandra-repl installed via the Imandra Installer, then run


and make sure it starts up successfully (i.e. all updates are installed). Once it's started, quit it again with Ctrl-D. Next:

npm install

to install the bucklescript compiler, imandra-prelude and Imandra client bindings for bucklescript. Then:

npm run watch

You may see a few errors the first time you run watch - this I believe is due to an issue with components in bsb.exe as they are a WIP. However, if you run npm run watch multiple times, you should stop seeing errors after a few builds, and from then on incremental compilation will work sucessfully.

The compilation chain

For runtime:

  • .iml and .ire files are compiled to .ml files using imandra-extract (which is bundled with the Imandra Installer), and integrated into the build via bsb components.
  • .ml and .re files are compiled to .bs.js via bsb itself.
  • Imandra_prelude is available automatically inside imandra-http-server
  • When compiling to javascript, Imandra_prelude is provided by imandra-prelude, added as an npm/bucklescript dependency.

Verification tests:

  • Tests are run via Jest on node.js using the compiled runtime JS files.
  • As part of the test run, the Imandra client bucklescript bindings (bs-imandra-client) are used to spin up imandra-http-server (which is bundled as part of the Imandra Installer), which is an OCaml binary talking to Imandra's reasoning engine in the cloud.
  • The HTTP Imandra client API is used to load .iml and .ire files into the running imandra-http-server OCaml process, and perform verification statements.
  • The verification results are captured and reported back as part of the Jest test run.

To run the verification goals:

npm run test

Viewing instances

Click here to see a quick example of viewing instances with Imandra

The TicTacToe example is hooked up to Imandra to allow querying and viewing instances. To start it, from the verified-react repo root run:

imandra-http-server -reason

to start Imandra's http server with reason syntax loaded. Then for bucklescript compilation, (in another terminal) run:

npm install
npm run watch

Then, to start the parcel.js dev server, (in another terminal) run:

npm run watch-tictactoe

You should now be able to visit http://localhost:1234 to see/play the TicTacToe game (verified via the npm run test Jest tests), and also query for instances from Imandra.

How it works

The TicTacToe UI is wrapped in an InstanceBrowser component, which loads the game logic into Imandra (along with some JSON encoders and decoders) via examples/tictactoe/Setup.ire.

The TicTacToe UI component has been edited slightly to allow a default intial state to be passed from its parent via the customInitialLogicState prop.

When the instance query box's contents change, the query is sent to imandra-http-server's /instance/by-src endpoint as a lambda expression, x : game_state => <constraint>, so an instance of type game_state matching the constraint is returned, printed to a JSON string via a serialisation function (instancePrinterFn).

This returned instance is then passed to the customInitialLogicState prop and rendered by the UI component.