message: Remove previous testbed output directories during clean.
diff: "license": "UNLICENSED",
  "scripts": {
  "build": "tsc && npm run copy:frontendpublic && npm run copy:testpublic",
  - "clean": "rimraf lib",
  + "clean": "rimraf lib && rimraf backend/lib && rimraf frontend/lib",
  "start": "floss --debug --path lib/testbed/frontend/index.js",
  "pretest": "npm run build",
  "test": "floss --path lib/testbed/frontend/index.js",
  