Unit test Android custom view with AndroidX Test and Robolectric

count_custom_view.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:padding="10dp"
    android:background="#50000000">

    <Button
        android:layout_width="@dimen/button_size"
        android:layout_height="60dp"
        android:id="@+id/buttonSubtract"
        android:textSize="@dimen/count_text_size"
        android:text="@string/button_subtract" />

    <TextView
        android:layout_width="100dp"
        android:layout_height="50dp"
        android:id="@+id/textView"
        android:text="0"
        android:gravity="center|bottom"
        android:padding="5dp"
        android:textSize="@dimen/count_text_size"
        android:textStyle="bold"
        android:textColor="@android:color/black" />

    <Button
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:id="@+id/buttonAdd"
        android:textSize="@dimen/count_text_size"
        android:text="@string/button_add" />
</LinearLayout>