Added assignment feature test

Part of #1107

package.json

@@ -10,13 +10,18 @@
   "dependencies": {},
   "devDependencies": {
     "addons-linter": "^0.15.14",
+    "chai": "^4.1.2",
     "deploy-txp": "^1.0.7",
     "eslint": "^3.17.1",
     "eslint-plugin-no-unsanitized": "^2.0.0",
     "eslint-plugin-promise": "^3.4.0",
     "htmllint-cli": "^0.0.5",
+    "jsdom": "^11.6.2",
     "json": "^9.0.6",
+    "mocha": "^5.0.0",
     "npm-run-all": "^4.0.0",
+    "sinon": "^4.2.2",
+    "sinon-chai": "^2.14.0",
     "stylelint": "^7.9.0",
     "stylelint-config-standard": "^16.0.0",
     "stylelint-order": "^0.3.0",
@@ -38,6 +43,7 @@
     "lint:html": "htmllint *.html",
     "lint:js": "eslint .",
     "package": "rm -rf src/web-ext-artifacts && npm run build && mv src/web-ext-artifacts/firefox_multi-account_containers-*.zip addon.xpi",
-    "test": "npm run lint"
+    "test": "npm run lint && mocha ./test/setup.js test/**/*.test.js",
+    "test-watch": "mocha ./test/setup.js test/**/*.test.js --watch"
   }
 }