### Question:
AnnotationListItem implements AnnotationListItemView.Presenter, IsWidget { @Override public void onCollapseChange( ) { if ( collapseChangeHandler != null ) { collapseChangeHandler.onCollapseChange( ); } } AnnotationListItem( ); @Inject  AnnotationListItem( AnnotationListItemView view, Instance<AnnotationValuePairListItem> itemInstance ); @Override Widget asWidget( ); void loadAnnotation( Annotation annotation, AnnotationSource annotationSource ); void setDeleteAnnotationHandler( AdvancedAnnotationListEditorView.DeleteAnnotationHandler deleteAnnotationHandler ); void setClearValuePairHandler( AdvancedAnnotationListEditorView.ClearValuePairHandler clearValuePairHandler ); void setEditValuePairHandler( AdvancedAnnotationListEditorView.EditValuePairHandler editValuePairHandler ); void setCollapseChangeHandler( AdvancedAnnotationListEditorView.CollapseChangeHandler collapseChangeHandler ); boolean isCollapsed( ); void setCollapsed( boolean collapsed ); void setReadonly( boolean readonly ); @Override void onDelete( ); @Override void onCollapseChange( );  }### Answer:
@Test public void testOnCollapseChange( ) { listItem.setCollapseChangeHandler( collapseChangeHandler ); listItem.onCollapseChange( ); verify( collapseChangeHandler, times( 1 ) ).onCollapseChange( ); }