Why doesn't composer remove remove package?

I have cloned a project written in Yii2. There are some extensions in vendor folder which I want to remove them from project.I am sure they are installed using composer because they are noted in composer.lock file.

Example structure in vendor:




I have tried " composer remove phpunit/phpunit " but nothing is removed. Why is it so?

Thank you.

What was the output of "composer removeā€¦"?