Add [buildkite] service (#1657)

* Support for buildkite

* Added to the examples as well

* Removed the unnecessary label property

* Fixed the example

* Improve the tests

* Made the branch optional and review suggestions

* Added network error test

* Unexpected response test

* PR review suggestions

* Updated test to include all responses

* Forgot one of the tests

services/buildkite/buildkite.tester.js

@@ -0,0 +1,42 @@
+'use strict';
+
+const Joi = require('joi');
+const ServiceTester = require('../service-tester');
+const t = new ServiceTester({ id: 'buildkite', title: 'Buildkite Builds' });
+const { invalidJSON } = require('../response-fixtures');
+module.exports = t;
+
+t.create('buildkite invalid pipeline')
+  .get('/unknown-identifier/unknown-branch.json')
+  .expectJSON({ name: 'build', value: 'not found' });
+
+t.create('buildkite valid pipeline')
+  .get('/3826789cf8890b426057e6fe1c4e683bdf04fa24d498885489/master.json')
+  .expectJSONTypes(Joi.object().keys({
+    name: 'build',
+    value: Joi.equal('failing', 'passing', 'unknown')
+  }));
+
+t.create('buildkite valid pipeline skipping branch')
+  .get('/3826789cf8890b426057e6fe1c4e683bdf04fa24d498885489.json')
+  .expectJSONTypes(Joi.object().keys({
+    name: 'build',
+    value: Joi.equal('failing', 'passing', 'unknown')
+  }));
+
+t.create('buildkite unknown branch')
+  .get('/3826789cf8890b426057e6fe1c4e683bdf04fa24d498885489/unknown-branch.json')
+  .expectJSON({ name: 'build', value: 'unknown' });
+
+t.create('buildkite connection error')
+  .get('/_.json')
+  .networkOff()
+  .expectJSON({ name: 'build', value: 'inaccessible' });
+
+t.create('buildkite unexpected response')
+  .get('/3826789cf8890b426057e6fe1c4e683bdf04fa24d498885489.json')
+  .intercept(nock => nock('https://badge.buildkite.com')
+    .get('/3826789cf8890b426057e6fe1c4e683bdf04fa24d498885489.json?branch=master')
+    .reply(invalidJSON)
+  )
+  .expectJSON({name: 'build', value: 'invalid'});