android-testing-runtime-permissions-showing-rationale

MainActivity.java

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,  
                                           @NonNull int[] grantResults) {
    if (requestCode == REQ_CODE_PERMISSIONS_READ_CONTACTS && grantResults.length > 0) {
        int grantResult = grantResults[0];
        if (grantResult == PackageManager.PERMISSION_GRANTED) {
            loadContacts();
        } else {
            isPermissionAlreadyDenied = true;
            if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.READ_CONTACTS)) {
                permissionDeniedRationaleView.setText(R.string.permission_denied_rationale_short);
            }
            permissionDeniedView.setVisibility(View.VISIBLE);
        }
    } else {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }
}