fix and re-enable companion test

package.json

@@ -102,7 +102,7 @@
     "test:unit": "jest",
     "test:companion": "cd ./packages/@uppy/companion && npm run test",
     "test:type": "tsc -p .",
-    "test": "npm run lint && npm run test:unit && npm run test:type",
+    "test": "npm run lint && npm run test:unit && npm run test:type && npm run test:companion",
     "test:watch": "jest --watch",
     "travis:deletecache": "travis cache --delete",
     "watch:css": "onchange 'packages/**/*.scss' --initial --verbose -- npm run build:css",

packages/@uppy/companion/test/__mocks__/purest.js

@@ -20,7 +20,7 @@ class MockPurest {
           kind: 'drive#fileList',
           etag: '"bcIyJ9A3gXa8oTYmz6nzAjQd-lY/eQc3WbZHkXpcItNyGKDuKXM_bNY"',
           items: [{ id: '0B2x-PmqQHSKdT013TE1VVjZ3TWs' }],
-          fileSize: 300
+          size: 300
         }
       }
       const body = responses[this.opts.providerName]