Expect and Allow are not stubbing Singleton methods

Question

I have an Utils class that looks something like this

module A
  class Utils
    class << self
      def foo(arg)
        return arg
      end
    end
  end
end

And I'm trying to stub the foo method but both allow and expect don't work and the method is called either way, what am I doing wrong on my spec?

I tried stubbing by doing

allow(A::Utils).to receive(:foo).and_return("test")
expect(A::Utils).to receive(:foo).and_return("test")