Welcome to our tests! unit tests are under the 'unit/' dir, function under 'functional/'. Some of the test cases in functional/ check the file operation among the different storage media. Therefore, insert SD Card media to the test device when running this instrumentation test if the device has SD Card slot. If SD Card is not inserted or supported, the test creates virtual SD Card and uses it instead. To run just small tests" adb shell am instrument -w -e debug false -e log false -e timeout_msec 300000 -e size small com.android.documentsui.tests/androidx.test.runner.AndroidJUnitRunner Replace '-e size small' with '-e size large'.