Ensure that error-in-post test is run (#1096)

* Ensure that error-in-post test is run

* fixup! adding t.plan(1) and removing beforeExit check

As per Github comment #1096 (comment)

test/error-in-post.js → test/error-in-post.test.js

@@ -4,8 +4,6 @@ const t = require('tap')
 const Fastify = require('..')
 const fastify = Fastify()
 
-let errored = false
-
 fastify.route({
   method: 'POST',
   path: '/jsonBody',
@@ -23,14 +21,10 @@ const reqOpts = {
 }
 
 process.on('uncaughtException', (err) => {
-  errored = true
   t.equal(err.message, 'kaboom')
 })
 
 fastify.inject(reqOpts, (e, res) => {
+  t.plan(1)
   t.fail('should not be called')
 })
-
-process.on('beforeExit', () => {
-  t.ok(errored)
-})