I recommend using the PHPUnit phar file. You can download version 4 like this
wget https://phar.phpunit.de/phpunit-4.8.21.phar
Please note that Magento's autoloader is very picky in since PHPUnit does some class_exists to detect if other packages
(like PHP_Invoker) are installed this will fail if those packages are not installed. Instead of dealing with this problem
the easiest solution is to have all those optional packages in place. Using the phar file is a great solution to this
because everything is bundled inside that phar.
The testcase do NOT rely on EcomDev_PHPUnit anymore since EcomDev_PHPUnit was doing way too much "magic" in the background. The showstopper definitly was that EcomDev_PHPUnit manages the configuration (and the fact that it's not caching) it which is critical for Aoe_Scheduler since job configuration can also live in config.
In addition to that the tests coming with Aoe_Scheduler are integration tests. That means some of them will actually trigger
scheduler.php and this is where we can't have a separate test environment the runs the tests if that same test environment
won't be available when executing the jobs.
Going back to plain PHPUnit reduces the complexity of testing significantly and allows to have cleaner and more stable test cases.
Please note that your tests will run on your main databases. It's not recommended to run the tests on a production database since jobs will be created, deleted and executed during the testing process