elif is_gen_callable(call) or is_async_gen_callable(call):
            solved = await solve_generator(
                call=call, stack=async_exit_stack, sub_values=solved_result.values
            )
        elif is_coroutine_callable(call):
            solved = await call(**solved_result.values)
        else:
            solved = await run_in_threadpool(call, **solved_result.values)

	if err != nil {
		return nil, toStorageErr(err)
	}
	return respBody, nil
}

// Wrapper to restClient.Call to handle network errors, in case of network error the connection is disconnected
// and a healthcheck routine gets invoked that would reconnect.
func (client *storageRESTClient) call(ctx context.Context, rpcMethod string, values url.Values, body io.Reader, length int64) (io.ReadCloser, error) {
	if values == nil {

	all = make([]*peerRESTClient, len(hosts))
	for i, host := range hosts {
		if host == nil {
			continue
		}
		all[i] = newPeerRESTClient(host, endpoints.FindGridHostsFromPeer(host))
		remote = append(remote, all[i])
	}
	if len(all) != len(remote)+1 {
		peersLogIf(context.Background(), fmt.Errorf("Expected number of all hosts (%v) to be remote +1 (%v)", len(all), len(remote)), logger.WarningKind)
	}

     *     {@link #whenAllComplete(Iterable)} or {@link #whenAllComplete(Iterable)}
     * @throws IllegalStateException if called outside of a call to {@link
     *     CombiningCallable#call(DeferredCloser, Peeker)} or {@link
     *     AsyncCombiningCallable#call(DeferredCloser, Peeker)}
     */
    @ParametricNullness
    public final <D extends @Nullable Object> D getDone(ClosingFuture<D> closingFuture)

    join();

    if (uncaughtThrowable != null) {
      throw new AssertionError("Uncaught throwable in " + getName(), uncaughtThrowable);
    }
  }

  /**
   * Causes this thread to call the named void method, and asserts that the call returns normally.
   */
  public void callAndAssertReturns(String methodName, Object... arguments) throws Exception {
    checkNotNull(methodName);
    checkNotNull(arguments);

    ListenableFuture<Boolean> future2 =
        serializer.submit(
            new Callable<Boolean>() {
              @Override
              public Boolean call() {
                return blockingCallable.isRunning();
              }
            },
            directExecutor());

An example could be that you have an external authentication provider that you need to call.

You send it a token and it returns an authenticated user.

This provider might be charging you per request, and calling it might take some extra time than if you had a fixed mock user for tests.

You probably want to test the external provider once, but not necessarily call it for every test that runs.

  public void testReturning() throws Exception {
    assertNull(Callables.returning(null).call());

    Object value = new Object();
    Callable<Object> callable = Callables.returning(value);
    assertSame(value, callable.call());
    // Expect the same value on subsequent calls
    assertSame(value, callable.call());
  }

  @J2ktIncompatible
  @GwtIncompatible
  public void testAsAsyncCallable() throws Exception {

            return (String) method.invoke(instance, message, possibleValues, defaultReply);
        } catch (Exception e) {
            throw new PrompterException("Unable to call prompter", e);
        }
    }

    @Override
    public String promptForPassword(String message) throws PrompterException {
        try {

    ListenableFuture<Boolean> future2 =
        serializer.submit(
            new Callable<Boolean>() {
              @Override
              public Boolean call() {
                return blockingCallable.isRunning();
              }
            },
            directExecutor());