### Question:
TabpageStreamApi extends BaseStreamApi implements NeovimTabpageApi { @Override public CompletableFuture<Boolean> isValid() { return sendWithResponseOfType(prepareMessage(IS_VALID), Boolean.class); } TabpageStreamApi(ReactiveRpcStreamer reactiveRpcStreamer, Tabpage model); @Override Tabpage get(); @Override CompletableFuture<List<NeovimWindowApi>> getWindows(); @Override CompletableFuture<NeovimWindowApi> getWindow(); @Override CompletableFuture<Object> getVar(String name); @Override CompletableFuture<Void> setVar(String name, Object value); @Override CompletableFuture<Void> deleteVar(String name); @Override CompletableFuture<Integer> getNumber(); @Override CompletableFuture<Boolean> isValid(); @Override String toString();  }### Answer:
@Test public void isValidTest() throws ExecutionException, InterruptedException { assertNormalBehavior( () -> CompletableFuture.completedFuture(new ResponseMessage(1, null, false)), () -> tabpageStreamApi.isValid(), request -> assertMethodAndArguments(request, NeovimTabpageApi.IS_VALID, tabpage), Assert::assertFalse ); assertErrorBehavior( () -> tabpageStreamApi.isValid(), request -> assertMethodAndArguments(request, NeovimTabpageApi.IS_VALID, tabpage) ); }