At the company I work with, our modules are individual repositories. We add those as composer packages to our Magento 2 installation by adding GitHub as a repository in our composer.json:

"require": {
    "vendor/custom-module": "dev-master"
},
"repositories": [
    {
      "type": "git",
      "url": "[email protected]:CompanyName/custom-module.git"
    }
],
"autoload": {
    "files": [
        "registration.php"
    ],
    "psr-4": {
        "Happy\\PrivateProducts\\": ""
    }
},

This works fine, no questions there.

The next thing we want to do is set these modules up as individual testable modules using a Continuous Integration provider (CircleCI in our case). So I've added dependencies like phpunit and phpcs to the composer.json of our module:

"require-dev": {
    "phpunit/phpunit": "5.3.5",
    "squizlabs/php_codesniffer": "1.5.3"
}

We setup our master-branch to be protected and do our work in the development-branch. When we want to merge the changes we send a pull request to our master-branch. This is the moment where CircleCI kicks in.

Everything gets installed properly on our CI servers' container that is spawned. However, when I try to run phpunit or phpcs from the command line (using vender/bin/phpunit or vendor/bin/phpcs for example), I get a PHP error that all kind of Magento dependencies are missing:

PHP Fatal error:  Uncaught Error: Class 'Magento\Framework\Component\ComponentRegistrar' not found in /home/ubuntu/custom-module/registration.php:6

Stack trace: #0 /home/ubuntu/custom-module/vendor/composer/autoload_real.php(66): require() #1 /home/ubuntu/custom-module/vendor/composer/autoload_real.php(56): composerRequiref6475a93b986d5b841accb13703f079a('bdaf00c9b7defe0...', '/home/ubuntu/ma...') #2 /home/ubuntu/custom-module/vendor/autoload.php(7): ComposerAutoloaderInitf6475a93b986d5b841accb13703f079a::getLoader() #3 /home/ubuntu/custom-module/vendor/phpunit/phpunit/phpunit(45): require('/home/ubuntu/ma...') #4 {main} thrown in /home/ubuntu/mage2-private-products/registration.php on line 6

My question

I have a fairly good idea of why I'm getting this error. After all, I have the registration.php in my composer.json autoload-property. However, I am wondering what's best practice here?

• Should I omit the registration.php from my composer.json-file?
• Should I include the complete Magento framework as dev-dependency? (I don't think so because my unit tests should mock everything).
• Some other solution / suggestion?

What are other peoples experiences / best practices when it comes to individual module testing / CI processes with Magento 2?