public void OnHttpClientUpgradeWithoutHandlerAdded()
{
var b = new Http2ConnectionHandlerBuilder();
b.FrameListener = new Http2FrameAdapter();
b.IsServer = false;
_handler = b.Build();
var e = Assert.Throws <Http2Exception>(() => _handler.OnHttpClientUpgrade());
Assert.Equal(Http2Error.InternalError, e.Error);
}