Using Codeception to run existing Laravel 5.1 PHPUnit tests

I have a number of tests written for a Laravel 5.1 application, and I'm currently using PHPUnit to run the tests. I'm attempting to investigate codeception as we have other applications that aren't built on Laravel, so codeception looks like the easiest way to get a similar interface for testing.

We have a reasonably large team, so I would prefer to use a single consistent command for testing across all projects instead of some using codecept and some using phpunit.

Here's what I've tried as my codeception.yml:

actor: Tester
paths:
   tests: tests
   log: storage/codeception/_output
   data: storage/codeception/_data
   support: storage/codeception/_support
   envs: storage/codeception/_envs

modules:
   enabled:
       - Laravel5:
           environment_file: .env

But I get this response:

$ codecept run
Codeception PHP Testing Framework v2.1.4
Powered by PHPUnit 4.8.18 by Sebastian Bergmann and contributors.

  [RuntimeException]           
  Suite '' could not be found

So my question is this:

How do I convince codeception to run my existing PHPUnit tests with as little modification as possible?