How to use PHPUnit on Docker in PHPStorm

PHPStorm Version: 2019.3.4

Specify CLI interpreter

Go to Settings > Languages & Frameworks > PHP

Select a interpreter from Docker
The result looks like this

Add testing framework configuration

Go to Settings > Languages & Frameworks > PHP > Test Frameworks
Select Configuration Type: PHPUnit by remote interpreter
Select the interpreter configured previously

The final result looks like this

Try it

Then you can see the test, try to run it.