refactor [cocoapods] service (#2977)

* refactor [cocoapods] service

* remove pointless default

* move join to render()

services/cocoapods/cocoapods-docs.tester.js

@@ -0,0 +1,28 @@
+'use strict'
+
+const Joi = require('joi')
+const { isIntegerPercentage } = require('../test-validators')
+
+const t = (module.exports = require('../tester').createServiceTester())
+
+t.create('doc percent (valid)')
+  .get('/AFNetworking.json')
+  .expectJSONTypes(
+    Joi.object().keys({
+      name: 'docs',
+      value: isIntegerPercentage,
+    })
+  )
+
+t.create('doc percent (null)')
+  .get('/AFNetworking.json')
+  .intercept(nock =>
+    nock('https://metrics.cocoapods.org')
+      .get('/api/v1/pods/AFNetworking')
+      .reply(200, '{"cocoadocs": {"doc_percent": null}}')
+  )
+  .expectJSON({ name: 'docs', value: '0%' })
+
+t.create('doc percent (not found)')
+  .get('/not-a-package.json')
+  .expectJSON({ name: 'docs', value: 'not found' })