Versioning with Mix, manifest does not exist

I am working on a branch (dev) where I have a package.json and composer.json with more updated versions than a branch called test (used for online tests) and when doing the merge inside the test branch, It does not merge these 2 files so it shows me an error of:

Versioning with Mix, manifest does not exist

because it gives me errors when doing npm run watch. I need to do the merge and be updated with what I have in my branch.

Package.json (Dev)

   {
  "private": true,
  "scripts": {
    "dev": "npm run development",
    "development": "cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js",
    "watch": "cross-env NODE_ENV=development node_modules/webpack/bin/webpack.js --watch --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js",
    "watch-poll": "npm run watch -- --watch-poll",
    "hot": "cross-env NODE_ENV=development node_modules/webpack-dev-server/bin/webpack-dev-server.js --inline --hot --config=node_modules/laravel-mix/setup/webpack.config.js",
    "prod": "npm run production",
    "production": "cross-env NODE_ENV=production node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js"
  },
  "devDependencies": {
    "axios": "^0.15.3",
    "bootstrap-sass": "^3.3.7",
    "cross-env": "^3.2.3",
    "jquery": "^3.1.1",
    "laravel-mix": "0.*",
    "lodash": "^4.17.4",
    "vue": "^2.1.10"
  }
}

Package.json (Test)

    {
  "private": true,
  "scripts": {
    "dev": "node node_modules/cross-env/bin/cross-env.js NODE_ENV=development node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js",
    "watch": "node node_modules/cross-env/bin/cross-env.js NODE_ENV=development node_modules/webpack/bin/webpack.js --watch --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js",
    "hot": "node node_modules/cross-env/bin/cross-env.js NODE_ENV=development node_modules/webpack-dev-server/bin/webpack-dev-server.js --inline --hot --config=node_modules/laravel-mix/setup/webpack.config.js",
    "production": "node node_modules/cross-env/bin/cross-env.js NODE_ENV=production node_modules/webpack/bin/webpack.js --progress --hide-modules --config=node_modules/laravel-mix/setup/webpack.config.js"
  },
  "devDependencies": {
    "axios": "^0.15.2",
    "bootstrap-sass": "^3.3.7",
    "jquery": "^3.1.0",
    "laravel-mix": "^0.6.0",
    "lodash": "^4.16.2",
    "vue": "^2.0.1"
  }
}

In test I need the .json of Dev