Add ES Modules recipe

Author: motss

docs/recipes/babel.md

@@ -81,7 +81,7 @@ By default AVA's stage-4 preset will convert ES module syntax to CommonJS. This
 }
 ```
 
-You'll have to use [`@std/esm`](https://github.com/standard-things/esm) so that AVA can still load your test files.
+You'll have to use [`@std/esm`](https://github.com/standard-things/esm) so that AVA can still load your test files. [See our recipe for details](./es-modules.md).
 
 ## Disable AVA's Babel pipeline
 

docs/recipes/es-modules.md

@@ -0,0 +1,47 @@
+# Using ES modules in AVA
+
+As of Node.js 8.5.0, [ES modules](http://2ality.com/2017/09/native-esm-node.html) are natively supported, but behind the `--experimental-modules` command line flag. It works using the `.mjs` file extension. AVA does not currently support the command line option or the new file extension, but you *can* use the [`@std/esm`](https://github.com/standard-things/esm) module to use the new syntax.
+
+Here's how you get it working with AVA.
+
+First, install [`@std/esm`](https://github.com/standard-things/esm):
+
+```
+$ npm install @std/esm
+```
+
+Configure it in your `package.json` file, and add it to AVA's `"require"` option as well. Make sure to add it as the first item:
+
+```json
+{
+	"ava": {
+		"require": [
+			"@std/esm"
+		]
+	},
+	"@std/esm": "js"
+}
+```
+
+By default AVA converts ES module syntax to CommonJS. [You can disable this](./babel.md#preserve-es-module-syntax).
+
+You can now use native ES modules with AVA:
+
+```js
+// sum.mjs
+export default function sum(a, b) {
+	return a + b;
+};
+```
+
+```js
+// test.js
+import test from 'ava';
+import sum from './sum.mjs';
+
+test('2 + 2 = 4', t => {
+	t.is(sum(2, 2), 4);
+});
+```
+
+Note that test files still need to use the `.js` extension.

readme.md

@@ -1140,6 +1140,7 @@ It's the [Andromeda galaxy](https://simple.wikipedia.org/wiki/Andromeda_galaxy).
 - [TypeScript](docs/recipes/typescript.md)
 - [Flow](docs/recipes/flow.md)
 - [Configuring Babel][Babel recipe]
+- [Using ES modules](docs/recipes/es-modules.md)
 - [Testing React components](docs/recipes/react.md)
 - [Testing Vue.js components](docs/recipes/vue.md)
 - [JSPM and SystemJS](docs/recipes/jspm-systemjs.md)