Codeception in mamp/bitnami stack

Hi, I’m having a little trouble setting up unit tests for the first time in yii 2.0. Also trying codeception for the first time time too. My dev environment is a bitnami stack of php and postgres sql. My site works fine front and back, no issues with db access but trying to run tests for the first time I’m getting a pdo driver not found message. At a guess its trying to use a machine set up rather than the stack. Does that sound likely? How can I force unit tests to use the stack environment?

I’ve changed the codecption config to point to the correct db/port but is this more a php environment issue? Thanks