docs: Add testing section

docs/testing.md

@@ -1,3 +1,93 @@
 # Testing
 
-_Coming soong_
+Mono is shipped with [mono-test-utils](https://github.com/terrajs/mono-test-utils), a powerful module to test your Mono API.
+
+```js
+const { start, stop, url, $get, $post, $put, $del } = require('mono-test-utils')
+```
+
+## Start Mono
+
+This module lets your start & stop your Mono server in different environements easily:
+
+```js
+const { app, server, conf, stdout, stderr } = await start(dir, options = {})
+```
+
+`stdout` and `stderr` are array of strings, useful to check logs values.
+
+## Stop Mono
+
+To stop Mono, simply call `stop` and giving the `server` send back by `start()`.
+
+```js
+await stop(server)
+```
+
+## HTTP requests
+
+Mono test utils gives mutliple methods to make HTTP requests to your Mono server:
+
+```js
+await $get(path, options = {})
+await $post(path, options = {})
+await $put(path, options = {})
+await $del(path, options = {}) // alias: `$delete`
+await $patch(path, options = {})
+await $head(path, options = {})
+await $options(path, options = {})
+```
+
+The `options` are the same as [request](https://github.com/request/request).
+
+Every of the following methods return an object with these properties:
+
+```js
+{
+  statusCode, // HTTP status code
+  headers, // Headers sent back
+  body, // Body of the response
+  stdout, // Logs written on stdout during the request
+  stderr // Logs written on stderr during the request
+}
+```
+
+## Example
+
+Example of `test/index.js` with [ava](https://github.com/avajs/ava):
+
+```js
+const test = require('ava')
+const { join } = require('path')
+
+const { start, stop, $get, $post } = require('mono-test-utils')
+
+let ctx
+
+// Start server
+test.before('Start Mono app', async (t) => {
+	ctx = await start(join(__dirname, 'fixtures/example/'))
+})
+
+// Test API Endpoints
+test('Call GET - /example', async (t) => {
+	const { stdout, stderr, statusCode, body } = await $get('/example')
+	t.true(stdout[0].includes('GET /example'))
+	t.is(stderr.length, 0)
+	t.is(statusCode, 200)
+  // Imagine that GET - /example returns { hello: 'world' }
+	t.deepEqual(body.body, { hello: 'world' })
+})
+
+test('Call POST - /example', async (t) => {
+	const { statusCode, body } = await $post('/example', {
+		body: { foo: 'bar' }
+	})
+	t.is(statusCode, 200)
+})
+
+// Close server
+test.after('Close Mono server', async (t) => {
+	await close(ctx.server)
+})
+```