add tap-spec to format output

test/render.test.js

@@ -3,6 +3,12 @@
 /* jshint node:true */
 
 var test = require('tape');
+var tapSpec = require('tap-spec');
+
+test.createStream()
+  .pipe(tapSpec())
+  .pipe(process.stdout);
+
 var mbgl = require('..');
 var fs = require('fs');
 var path = require('path');