Magento 2.3 added app/code/magento modules after 2.3 update (with sample data)

Question

I recently update a site to 2.3 (with sample data enabled) no I find a lot of TestModules in the app/code/magento folder. I have 4 questions regarding these modules:

1. Do they come from the 2.3 update or do they come from the sample data?
2. Can I remove them?
3. Can I git ignore them because they came after composer update?
4. Is there a way so they do not get installed with composer?

Answer 1

1. The test modules are a part of UnitTesting (https://phpunit.de/)
2. You could as far as i know but i would recommend just ignoring them
3. you could git ignore them but the exact command i would need to search
4. Same thing as 3

Unit testing is a big part of Magento and you will need them if you ever wanted to do that. I do get you do not want files you might not need and they serve no other purpose other then UnitTesting the code.

Answer 2

These modules are probably created because of unit tests. See the following issue: https://github.com/magento/magento2/issues/12696