Add PHPUnit internal helper(s)

[stloyd]

We often start to do copy-paste work in tests, thus we should begin to have some reusable helpers to make our internal tests easier to maintain.

Helpers:

• FilesystemHelper with: create, delete for files & directories,
• ...

[Bellangelo]

Hi @norberttech , I would like to help on this. If I am not mistaken there isn't any generic place to create the new helpers. Should we create a tests directory at the root for this case?

[norberttech]

hey @Bellangelo, awesome! I think I would put it inside of the src/core/etl/src/Flow/ETL/Test/... so it can be installed with ETL package together

[Bellangelo]

@norberttech, i checked and the Filesystem issue that the original PR was addressing seems to be fixed. I checked a little bit around the project and I noticed that some of the Extractor's tests logic is duplicated so I created a PR for it #1291. Not sure if all the changes are needed but it is a start.

Also, since the description of this issue does not contain much info I would really appreciate it if you could add what it is missing currently.

[norberttech]

Since this task was never properly explained, here is a proper description of what we are trying to achieve here:

#1291 (comment)