[Q] What's the difference between running traditional tests and using the Yii module?

[igorsantos07]

I'm new to functional testing and got confused when reading about the Yii module documentation.
What's the difference between running tests using the module and not using?

I thought at first that the tests would load the page and work on them as a user would (externally), instead of dealing with the page inside the test's code - what would trigger issues with header and exit calls as stated.

I guess running the tests that way would be more resource intensive and slow? Is it that bad the way we currently have to test Yii apps?

Would there be a way to integrate the tests generated by the framework with Codeception instead?