1## Sprout 🌱2React Forget test framework that executes compiler fixtures.34Currently, Sprout runs each fixture with a known set of inputs and annotations. Sprout compares execution outputs (i.e. return values and console logs) of original source code and the corresponding Forget-transformed version.5We hope to add fuzzing capabilities to Sprout, synthesizing sets of program inputs based on type and/or effect annotations.67Sprout is now enabled for all fixtures! If Sprout cannot execute your fixture due to some technical limitations, add your fixture to [`SproutTodoFilter.ts`](./src/SproutTodoFilter.ts) with a comment explaining why.89### Sprout CLI10Sprout is now run as a part of snap, except when in filter mode.1112### Adding fixtures to Sprout1314#### 1. Annotate fixtures.15Each fixture test executed by Sprout needs to export const `FIXTURE_ENTRYPOINT` object with the following type signature.1617```js18type FixtureEntrypoint<T> = {19  // function to be invoked20  fn: ((...params: Array<T>) => any),21  // params to pass to fn22  // (if `fn` is a react component, this should be an array23  // with exactly one element -- props)24  params: Array<T>,25}26```2728Example:29```js30// test.js31function MyComponent(props) {32  return <div>{props.a + props.b}</div>;33}34export const FIXTURE_ENTRYPOINT = {35  fn: MyComponent,36  params: [{a: "hello ", b: "world"}],37};38```3940#### 2. Import / define helper functions.4142- Prefer importing helper functions for readability and simplicity.43- Fixtures that require helper functions with specific types or mutability can define their own within the same fixture file.4445```js46// test.js47import { addOne } from 'shared-runtime';4849function customHelper(val1, val2) {50  // This directive is important, as helper functions don't51  // always follow the rules of React.52  "use no forget";53  // ...54}5556// ...57```5859#### Notes60- If your fixture needs to import from an external module, we currently only support importing from `react` (see Milestones todo list).6162- Any fixture can use React hooks, but they need to be first imported. We may later enforce that only `isComponent: true` fixtures can use React hooks.63    ```ts64    import {useState} from 'react';65    ```6667- If your fixture wants to export multiple functions to Sprout to run, please split up the fixture into multiple files (e.g. `test-case-1`, `test-case-2`, etc).6869- Sprout currently runs each fixture in an iife to prevent variable collisions, but it does not run fixtures in isolation. Please do not mutate any external state in fixtures.7071- Sprout does not run fixtures listed in [`SproutTodoFilter.ts`](./src/SproutTodoFilter.ts), even in filter mode.7273### Milestones:74- [✅] Render fixtures with React runtime / `testing-library/react`.75- [✅] Make Sprout CLI -runnable and report results in process exit code.76- [✅] Enable Sprout by default and run it in the Github Actions pipeline.77- [🚧] Make all existing test fixtures Sprout compatible (see `SproutTodoFilter.ts`). This involves each fixture being annotated with `FIXTURE_ENTRYPOINT` and using shared functions and/or defining its own helpers.78  - 77 done, ~410 to go79- [✅] *(optional)* Store Sprout output as snapshot files. i.e. each fixture could have a `fixture.js`, `fixture.snap.md`, and `fixture.sprout.md`.80- [✅] Add support for `fbt`.