Core: Consider upgrading PHPUnit version notice

[peter279k]

Feature Request

• According to this issue, the @expectedException annotation will be deprecated in future PHPUnit versions.
• According official PHPUnit site, the PHPUnit 6 version supports php-7.0, and it's not supported currently.
  Using PHPUnit 7 or PHPUnit 8 instead.

Suggested solution

• Upgrading the PHPUnit version to 7 or 8 if possible.
  And it seems that this project still supports php-7.1, I think it's proper to use PHPUnit 7.
• The @expectedException will be deprecated. Using the expectException method instead.

Once this issue is accepted, I would be happy to do this and create related PR :).

[luceos]

Yeah this makes a lot of sense. Especially because we already went to php 7.1. Feel free to send in a pr for this.

Thank you for pointing this out 👍

[franzliedke]

I've taken care of the deprecated annotation. We're already running PHPUnit 7.