Trade Federation uses an abstraction called
run tests. This abstraction objectifies the lowest-common-denominator Android device:
- It has a serial number
- It has a state: Online, Available, Recovery, or Not Available
- It has some notion of reliability. For instance, if we run a command, we can differentiate between the case where the command hasn't finished yet, the case where the device doesn't support running commands, and the case where the device has become unresponsive while running the command.
Different Classes of Devices
The three primary implementations of
ITestDevice represent three common
This is an actual piece of hardware, connected to the TF host machine either by USB, or by using
adb's TCP feature. The TestDevice class sits atop the ddmlib library, which is a Java interface to adb. So any
physical device listed in
adb devices can be instantiated and used as a
Emulators are handled specially by TF because they live in another process. To interact with an
Emulator, specify the
--emulator argument for the command. See
SdkAvdPreparer for more info.
Suppose you have a test that doesn't interact with a device at all. For instance, it might just
download a file from some service and verify that the file itself is valid. The
NullDevice is an
ITestDevice that is just a stub. It has a serial number like
null-device-N, and most attempted operations either no-op silently or throw.