test (ci): custom-parser.test.js is randomly failing with a 503 Service Unavailable

[darkgl0w]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the issue has not already been raised

Issue

Hello.

Following this #3622 (comment) - Failed CI Run Log.

This test is randomly failing on fastify CI runs returning a 503 HTTP Status code instead of the expected 200 at line 1381.

fastify/test/custom-parser.test.js

Lines 1317 to 1386 in ee795d3

	test('contentTypeParser should add multiple custom parsers with RegExp values', t => {
	t.plan(10)
	const fastify = Fastify()
	fastify.post('/', (req, reply) => {
	reply.send(req.body)
	})
	fastify.addContentTypeParser(/.*\+json$/, function (req, payload, done) {
	jsonParser(payload, function (err, body) {
	done(err, body)
	})
	})
	fastify.addContentTypeParser(/.*\+xml$/, function (req, payload, done) {
	done(null, 'xml')
	})
	fastify.addContentTypeParser(/.*\+myExtension$/, function (req, payload, done) {
	let data = ''
	payload.on('data', chunk => { data += chunk })
	payload.on('end', () => {
	done(null, data + 'myExtension')
	})
	})
	fastify.listen(0, err => {
	t.error(err)
	sget({
	method: 'POST',
	url: 'http://localhost:' + fastify.server.address().port,
	body: '{"hello":"world"}',
	headers: {
	'Content-Type': 'application/vnd.hello+json'
	}
	}, (err, response, body) => {
	t.error(err)
	t.equal(response.statusCode, 200)
	t.same(body.toString(), JSON.stringify({ hello: 'world' }))
	})
	sget({
	method: 'POST',
	url: 'http://localhost:' + fastify.server.address().port,
	body: '{"hello":"world"}',
	headers: {
	'Content-Type': 'application/test+xml'
	}
	}, (err, response, body) => {
	t.error(err)
	t.equal(response.statusCode, 200)
	t.same(body.toString(), 'xml')
	})
	sget({
	method: 'POST',
	url: 'http://localhost:' + fastify.server.address().port,
	body: 'abcdefg',
	headers: {
	'Content-Type': 'application/+myExtension'
	}
	}, (err, response, body) => {
	t.error(err)
	t.equal(response.statusCode, 200)
	t.same(body.toString(), 'abcdefgmyExtension')
	fastify.close()
	})
	})
	})

Possible fix: darkgl0w@e8a138c

Switching from simple-get to await fastify.inject, using teardown() to close the server, and making use of an async/await tap callback seems to solve the issue (needs to be confirmed by a couple runs on fastify CI).