Multi-target preparers

Similar to a target preparer, a multi-target preparer allows setup of multiple devices together. For example, this would be used when connecting two devices with Bluetooth for testing.

Base interface

The base interface is IMultiTargetPreparer, which allows implementing a setUp method to be executed. We recommend implementing our basic abstract class BaseMultiTargetPreparer, which provides a built-in disablement feature to easily disable a preparer.

Multi-target preparers also directly provide a tearDown method for any cleanup operation.


We recommend limiting each preparer to a single main function. This allows for easier reuse of preparers.

Also check the list of available preparers before adding a new one, to avoid duplicating work. Preparers are available in tools/tradefederation/core/src/com/android/tradefed/targetprep/multi/.

There's no limit to the number of devices that a multi-target preparer can set up. All the devices are available in IInvocationContext of the interface to implement.

XML configuration

The object tag is multi_target_preparer, for example:

<multi_target_preparer class="">

Operation order

  1. multi_target_preparer executes setUp after target_preparer.
  2. multi_target_preparer executes tearDown before target cleaners.

This doesn't always allow for performance of all setup steps, so it's possible in the XML to define the multi-target preparer as multi_pre_target_preparer and execute it before target_preparer instances.

<multi_pre_target_preparer class="">

The overall operation order is as followed:

  1. multi_pre_target_preparer setUp
  2. target_preparer setUp
  3. multi_target_preparer setUp
  4. multi_target_preparer tearDown
  5. target_preparer tearDown
  6. multi_pre_target_preparer tearDown

Any multi-target preparer can be declared as multi_target_preparer or multi_pre_target_preparer depending of what order of setup is required.