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

Author: lindsaylevine

.github/workflows/test.yml

@@ -27,4 +27,6 @@ jobs:
         with:
           node-version: ${{ matrix.node-version }}
       - run: npm install
+      - run: cd test/fixtures/sample && npm install
+      - run: cd test/fixtures/sample && npm run build
       - run: npm test

.prettierignore

@@ -19,3 +19,4 @@ node_modules
 # Test
 __mocks__
 sample
+test/fixtures/next_dist 

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",