Run an instrument test from within app and wait for result

I am developing a QA automation solution that can record/playback QA tests on Android. A key business requirement is to have no dependency on a connected PC while playing back the recorded test. To that end, I'm trying to run an Instrumentation test without a connected PC. (Specifically, an Appium UiAutomator2 test).

My current approach is trying to run the test programmatically from my app. If I were running the test normally from a connected PC, I would use the command adb shell am instrument -w. I tried accessing ADB Shell from my app and running am instrument -w, but this produces an error that I am missing the INTERACT_ACROSS_USERS_FULL permission.

To get around this issue, I am trying to run the test using startInstrumentation. This successfully starts the test. However, the test immediately crashes. Upon further investigation, I traced the crash to an NPE: the test is trying to retrieve InstrumentationRegistry.getInstrumentation.getUiAutomation(0), but this returns null.

How do I run the test programatically and give it access to the required UiAutomation instance?

This is how I start the test:

public void runTest() {
    final String pm = getPackageName().replaceFirst(".test$", "");
    final InstrumentationInfo info = getInstrumentationInfo(pm);
    if (info != null) {

        final ComponentName cn = new ComponentName(info.packageName,
                info.name);

        Bundle arguments = new Bundle();
        arguments.putString("class", "io.testim.appiumwrapper.test.AppiumUiAutomator2Server");
        //cn = {io.extension.test/android.support.test.runner.AndroidJUnitRunner}
        startInstrumentation(cn, null, arguments);

    } 
}

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