class Mocha::YieldParameters

def add(*parameter_groups)
  @parameter_groups << parameter_groups.map do |pg|
    pg.is_a?(Array) ? pg : [pg]
  end
end

def initialize
  @parameter_groups = []
end

def next_invocation
  case @parameter_groups.length
  when 0 then []
  when 1 then @parameter_groups.first
  else @parameter_groups.shift
  end
end