mock.cr

macro mockable_method(type, method)
  class {{type}}
    def {{method.id}}
      if _mock = @_mock_{{method.id}}
        _mock.call
      else
        previous_def
      end
    end

    def _mock_{{method.id}}(&@_mock_{{method.id}} : -> _)
    end
  end
end


class Object
  macro method_missing(name, args, block)
    {% if name.starts_with?("_mock_") %}
      def {{name.id}}(&@_mock_{{name.id}} : -> _)
      end
    {% else %}
      {% previous_def %}
    {% end %}
  end
end

macro mock(var, method)
  x._mock_{{method.id}} do
    {{yield}}
  end
end

class Foo
  def coco
    1
  end

  def coco2(x, y)
    x + y
  end
end

# mockable_method Foo, coco
# mockable_method Foo, coco2 { |x, y| }

x = Foo.new
puts x.coco
puts x.coco2(10, 20)

x = Foo.new
mock(x, coco) do
  2
end
mock(x, coco2) do |a, b|
  a * b
end
# puts x.coco
# puts x.coco2(10, 20)