Can't run phpunit tests from command line

I am trying to run unit tests in a new laravel 5 application, using the phpunit framework. In the root path of my laravel application I ru the following command:

./vendor/bin/phpunit /tests/ExampleTest.php

And then I get the following message:

You need to set up the project dependencies using the following commands:
wget http://getcomposer.org/composer,phar
php composer.phar install

I already have composer installed in may system and I install Laravel 5 using composer. Isn't phpunit installed when I install a new laravel 5 application? If not, how can I install it in a existent laravel 5 application?

I known that I can also install phpunit globaly and resolve the problem. But maybe it will be a duplication since I have all the phpunit code already in may laravel application.