test(fixture): improve finding ports to reduce flaky

package.json

@@ -150,6 +150,7 @@
     "form-data": "4.0.0",
     "fs-extra": "9.0.0",
     "get-port": "5.1.1",
+    "get-port-please": "3.1.1",
     "glob": "7.1.6",
     "gzip-size": "5.1.1",
     "html-validator": "5.1.18",

test/lib/next-test-utils.ts

@@ -13,6 +13,7 @@ import path from 'path'
 import spawn from 'cross-spawn'
 import { writeFile } from 'fs-extra'
 import getPort from 'get-port'
+import { getRandomPort } from 'get-port-please'
 import fetch from 'node-fetch'
 import qs from 'querystring'
 import treeKill from 'tree-kill'
@@ -171,7 +172,18 @@ export function renderViaHTTP(
 }
 
 export function findPort() {
-  return getPort()
+  // [NOTE] What are we doing here?
+  // There are some flaky tests failures caused by `No available ports found` from 'get-port'.
+  // This may be related / fixed by upstream https://github.com/sindresorhus/get-port/pull/56,
+  // however it happened after get-port switched to pure esm which is not easy to adapt by bump.
+  // get-port-please seems to offer the feature parity so we'll try to use it, and leave get-port as fallback
+  // for a while until we are certain to switch to get-port-please entirely.
+  try {
+    return getRandomPort()
+  } catch (e) {
+    require('console').warn('get-port-please failed, falling back to get-port')
+    return getPort()
+  }
 }
 
 export interface NextOptions {