### Question:
ActivityDataIOEditorWidgetViewImpl extends Composite implements ActivityDataIOEditorWidgetView { @EventHandler("addVarButton") public void handleAddVarButton(final ClickEvent e) { presenter.handleAddClick(); }  @Override void init(final Presenter presenter); @Override void showOnlySingleEntryAllowed(); @Override int getAssignmentsCount(); @Override void setTableTitleInputSingle(); @Override void setTableTitleInputMultiple(); @Override void setTableTitleOutputSingle(); @Override void setTableTitleOutputMultiple(); @Override void setProcessVarAsSource(); @Override void setProcessVarAsTarget(); @Override void setTableDisplayStyle(); @Override void setNoneDisplayStyle(); @Override void setAssignmentRows(final List<AssignmentRow> rows); @Override List<AssignmentRow> getAssignmentRows(); @Override AssignmentListItemWidgetView getAssignmentWidget(final int index); @Override void setReadOnly(final boolean readOnly); @EventHandler("addVarButton") void handleAddVarButton(final ClickEvent e);  }### Answer:
@Test public void testHandleAddVarButton() { view.init(presenter); view.handleAddVarButton(mock(ClickEvent.class)); verify(presenter, times(1)).handleAddClick(); }