After that you must delete the phpunit alias created by Homestead installation.
Just modify the file ~/.homestead/aliases and delete the line corresponding to phpunit
ex: alias phpunit="vendor/bin/phpunit"
Then you have to delete the alias saved in your system "memory" or "profile" by typing the following command in your terminal:
If everything went ok, you can now use phpunit from command line and to verify that it works correctly just type in your terminal:
It should show you the current phpunit version installed on your system.
Tested in homestead 0.7 on macOS 10.12