### Question:
HeaderMixin implements Mixin { public void setText(int title) { final TextView titleView = getTextView(); if (titleView != null) { titleView.setText(title); } } HeaderMixin(
      @NonNull TemplateLayout layout, @Nullable AttributeSet attrs, @AttrRes int defStyleAttr); TextView getTextView(); void setText(int title); void setText(CharSequence title); CharSequence getText();  }### Answer:
@Test public void testSetText() { HeaderMixin mixin = new HeaderMixin(mTemplateLayout, null, 0); mixin.setText("Foobar"); assertEquals("Foobar", mHeaderTextView.getText()); }