Add a GitHub project badge for Hacktoberfest [GithubHacktoberfest] (#4109)

services/github/github-hacktoberfest.tester.js

@@ -0,0 +1,26 @@
+'use strict'
+
+const Joi = require('@hapi/joi')
+const t = (module.exports = require('../tester').createServiceTester())
+
+const isHactoberfestCombinedStatus = Joi.string().regex(
+  /^[0-9]+ open issues?(, [0-9]+ PRs?)?(, [0-9]+ days? left)?$/
+)
+
+t.create('GitHub Hacktoberfest combined status')
+  .get('/badges/shields.json')
+  .expectBadge({
+    label: 'hacktoberfest',
+    message: isHactoberfestCombinedStatus,
+  })
+
+t.create('GitHub Hacktoberfest combined status (suggestion label override)')
+  .get(
+    `/badges/shields.json?suggestion_label=${encodeURIComponent(
+      'good first issue'
+    )}`
+  )
+  .expectBadge({
+    label: 'hacktoberfest',
+    message: isHactoberfestCombinedStatus,
+  })