Pretty much what the title says. The Page class's implementation of method_missing doesn't forward the code block. This stops Capybara's "within" method from working. It looks like this can easily be fixed by adding it to the list of parameters, and passing it in the send method:
def method_missing name, *args, &block
method_name = name.to_sym
return super unless browser.respond_to?(method_name)
browser.send(method_name, *args, &block)
end
This works in a simple trial, but I haven't checked anything else.