update next-on-netlify testing to use sample/.next dist

Author: lindsaylevine

package.json

@@ -34,6 +34,7 @@
   "devDependencies": {
     "@netlify/eslint-config-node": "^0.3.0",
     "cpx": "^1.5.0",
+    "execa": "^4.1.0",
     "husky": "^4.3.0",
     "jest": "^26.6.1",
     "path-exists": "^4.0.0",
@@ -56,7 +57,8 @@
   "jest": {
     "testMatch": [
       "**/test/**/*.js",
-      "!**/test/fixtures/**"
+      "!**/test/fixtures/**",
+      "!**/test/helpers/**"
     ],
     "verbose": true
   }