module Aws::ClientStubs

def next_stub(context)
  operation_name = context.operation_name.to_sym
  stub = @stub_mutex.synchronize do
    stubs = @stubs[operation_name] || []
    case stubs.length
    when 0 then default_stub(operation_name)
    when 1 then stubs.first
    else stubs.shift
    end
  end
  Proc === stub ? convert_stub(operation_name, stub.call(context)) : stub
end