assert documentation exists when mapboxjs version is bumped

package.json

@@ -21,7 +21,7 @@
     "sanitize-caja": "0.1.4"
   },
   "scripts": {
-    "test": "eslint src && phantomjs node_modules/mocha-phantomjs-core/mocha-phantomjs-core.js test/index.html",
+    "test": "eslint src && phantomjs node_modules/mocha-phantomjs-core/mocha-phantomjs-core.js test/index.html && mocha test/docs.js",
     "prepublishOnly": "npm run build",
     "build": "make"
   },

test/docs.js

@@ -0,0 +1,15 @@
+// makes sure documentation is generated when `mapboxjs: v#.#.#` is updated in _config.publisher-production.yml
+var fs = require('fs');
+var jsyaml = require('js-yaml');
+var assert = require('assert');
+
+// get mapbox.js version from config
+var config = fs.readFileSync('./_config.publisher-production.yml');
+var yaml = jsyaml.load(config);
+var mapboxjs = yaml.mapboxjs;
+// assert that that docs/_posts/api/v#.#.# exists
+describe('Documentation is generated', function() {
+  it('Documentation for ' + mapboxjs + ' exists', function() {
+    assert.equal(fs.existsSync('./docs/_posts/api/' + mapboxjs), true);
+  });
+});