Add test for incorrect costumes attribute in sb2 project

test/fixtures/sb2/invalid-costumes.json

@@ -0,0 +1,23 @@
+{
+   "objName": "Stage",
+   "sounds": [{
+           "soundName": "pop",
+           "soundID": -1,
+           "md5": "83a9787d4cb6f3b7632b4ddfebf74367.wav",
+           "sampleCount": 258,
+           "rate": 11025,
+           "format": ""
+       }],
+   "costumes": {
+       "invalid": "This should be an array but is an object instead"
+   },
+   "currentCostumeIndex": 0,
+   "penLayerMD5": "5c81a336fab8be57adc039a8a2b33ca9.png",
+   "penLayerID": -1,
+   "children": [],
+   "info": {
+       "videoOn": false,
+       "scriptCount": 0,
+       "spriteCount": 0
+   }
+}

test/unit/sb2.js

@@ -2,6 +2,9 @@ const fs = require('fs');
 const path = require('path');
 const test = require('tap').test;
 const analysis = require('../../lib/index');
+// using the sb2 directly to bypass scratch-parser and excersise
+// logic targeting broken project files
+const sb2 = require('../../lib/sb2');
 
 const defaultObject = fs.readFileSync(
     path.resolve(__dirname, '../fixtures/sb2/default.json')
@@ -13,6 +16,10 @@ const complexBinary = fs.readFileSync(
     path.resolve(__dirname, '../fixtures/sb2/complex.sb2')
 );
 
+const invalidCostumes = fs.readFileSync(
+    path.resolve(__dirname, '../fixtures/sb2/invalid-costumes.json')
+);
+
 test('default (object)', t => {
     analysis(defaultObject, (err, result) => {
         t.ok(typeof err === 'undefined' || err === null);
@@ -284,3 +291,18 @@ test('complex (binary)', t => {
         t.end();
     });
 });
+
+test('stage with invalid costumes', t => {
+    const project = JSON.parse(invalidCostumes);
+
+    sb2(project, (err, result) => {
+        t.ok(typeof err === 'undefined' || err === null);
+        t.type(result, 'object');
+        t.type(result.backdrops, 'object');
+        t.equal(result.backdrops.count, 0);
+        t.same(result.backdrops.id, []);
+        t.same(result.backdrops.hash, []);
+
+        t.end();
+    });
+});