DriverTestCreateBase create a base driver and verify.

DriverTestCreateEmpty creates an new image and verifies it is empty and the right metadata.

DriverTestCreateSnap Create a driver and snap and verify.

GetDriver create a new driver with given name or return a existing driver with the name updating the reference count.

InitLoopbacks ensures that the loopback devices are properly created within the system running the device mapper tests.

PutDriver removes the driver if it is no longer used and updates the reference count.

Driver conforms to graphdriver.Driver interface and contains information such as root and reference count of the number of clients using it.