Split up [github] testers (#2560)

- Update github contributors badge for `create-service-tester`.

services/github/github-languages.tester.js

@@ -0,0 +1,51 @@
+'use strict'
+
+const Joi = require('joi')
+const ServiceTester = require('../service-tester')
+const { isFileSize } = require('../test-validators')
+
+const t = (module.exports = new ServiceTester({
+  id: 'GithubLanguages',
+  title: 'GithubLanguages',
+  pathPrefix: '/github/languages',
+}))
+
+t.create('top language')
+  .get('/top/badges/shields.json')
+  .expectJSONTypes(
+    Joi.object().keys({
+      name: 'javascript',
+      value: Joi.string().regex(/^([1-9]?[0-9]\.[0-9]|100\.0)%$/),
+    })
+  )
+
+t.create('top language with empty repository')
+  .get('/top/pyvesb/emptyrepo.json')
+  .expectJSON({ name: 'language', value: 'none' })
+
+t.create('language count')
+  .get('/count/badges/shields.json')
+  .expectJSONTypes(
+    Joi.object().keys({
+      name: 'languages',
+      value: Joi.number()
+        .integer()
+        .positive(),
+    })
+  )
+
+t.create('language count (repo not found)')
+  .get('/count/badges/helmets.json')
+  .expectJSON({
+    name: 'languages',
+    value: 'repo not found',
+  })
+
+t.create('code size in bytes for all languages')
+  .get('/code-size/badges/shields.json')
+  .expectJSONTypes(
+    Joi.object().keys({
+      name: 'code size',
+      value: isFileSize,
+    })
+  )