I did as follows
1) Creating a styleable
Your described android:id is set to app:linkedView="@+id/tvTest. However, @+id/tvTest is used to create a new id with name "tvTest". What you want to do is use app:linkedView="@id/tvTest.
android:id
app:linkedView="@+id/tvTest
@+id/tvTest
app:linkedView="@id/tvTest