$ adb shell am instrument -w com.android.settings.tests/android.support.test.runner.AndroidJUnitRunner
To run all tests in a specific class:
$ adb shell am instrument -w -e class com.android.managedprovisioning.<class> com.android.managedprovisioning.tests/android.test.InstrumentationTestRunner
To run a specific test:
$ adb shell am instrument -w -e class com.android.settings.<class> com.android.settings.tests/android.support.test.runner.AndroidJUnitRunner