### Question:
DMNDiagramEditor extends AbstractProjectDiagramEditor<DMNDiagramResourceType> { public void onDataTypePageNavTabActiveEvent(final @Observes DataTypePageTabActiveEvent event) { kieView.getMultiPage().selectPage(DATA_TYPES_PAGE_INDEX); } @Inject  DMNDiagramEditor(final View view,
                            final TextEditorView xmlEditorView,
                            final ManagedInstance<SessionEditorPresenter<EditorSession>> editorSessionPresenterInstances,
                            final ManagedInstance<SessionViewerPresenter<ViewerSession>> viewerSessionPresenterInstances,
                            final Event<OnDiagramFocusEvent> onDiagramFocusEvent,
                            final Event<OnDiagramLoseFocusEvent> onDiagramLostFocusEvent,
                            final Event<NotificationEvent> notificationEvent,
                            final ErrorPopupPresenter errorPopupPresenter,
                            final DiagramClientErrorHandler diagramClientErrorHandler,
                            final @DMNEditor DocumentationView documentationView,
                            final DMNDiagramResourceType resourceType,
                            final DMNEditorMenuSessionItems menuSessionItems,
                            final ProjectMessagesListener projectMessagesListener,
                            final ClientTranslationService translationService,
                            final @DMNEditor ClientProjectDiagramService projectDiagramServices,
                            final Caller<ProjectDiagramResourceService> projectDiagramResourceServiceCaller,
                            final SessionManager sessionManager,
                            final SessionCommandManager<AbstractCanvasHandler> sessionCommandManager,
                            final Event<RefreshFormPropertiesEvent> refreshFormPropertiesEvent,
                            final DecisionNavigatorDock decisionNavigatorDock,
                            final LayoutHelper layoutHelper,
                            final OpenDiagramLayoutExecutor openDiagramLayoutExecutor,
                            final DataTypesPage dataTypesPage,
                            final IncludedModelsPage includedModelsPage,
                            final DMNEditorSearchIndex editorSearchIndex,
                            final SearchBarComponent<DMNSearchableElement> searchBarComponent,
                            final MonacoFEELInitializer feelInitializer,
                            final @DMNEditor ReadOnlyProvider readOnlyProvider,
                            final DRDNameChanger drdNameChanger, final LazyCanvasFocusUtils lazyCanvasFocusUtils); @Override @PostConstruct void init(); @OnStartup void onStartup(final ObservablePath path,
                          final PlaceRequest place); @Override void initialiseKieEditorForSession(final ProjectDiagram diagram); @Override void showDocks(); @Override Annotation[] getDockQualifiers(); @Override void hideDocks(); void onMultiPageEditorSelectedPageEvent(final @Observes MultiPageEditorSelectedPageEvent event); void onRefreshFormPropertiesEvent(final @Observes RefreshFormPropertiesEvent event); void onDataTypePageNavTabActiveEvent(final @Observes DataTypePageTabActiveEvent event); @Override void open(final ProjectDiagram diagram,
                     final Viewer.Callback callback); @OnOpen void onOpen(); @OnClose @Override void onClose(); @Override void onDiagramLoad(); @OnFocus void onFocus(); @OnLostFocus void onLostFocus(); @Override @WorkbenchPartTitleDecoration IsWidget getTitle(); @Override @WorkbenchPartTitle String getTitleText(); @Override @WorkbenchMenu void getMenus(final Consumer<Menus> menusConsumer); @Override @WorkbenchPartView IsWidget getWidget(); @OnMayClose boolean onMayClose(); @Override String getEditorIdentifier(); @Override boolean isReadOnly(); void onDataTypeEditModeToggle(final @Observes DataTypeEditModeToggleEvent event); static final String EDITOR_ID; }### Answer:
@Test public void testOnDataTypePageNavTabActiveEvent() { diagramEditor.onDataTypePageNavTabActiveEvent(mock(DataTypePageTabActiveEvent.class)); verify(multiPage).selectPage(DATA_TYPES_PAGE_INDEX); }