我正在尝试为类的任何实例（通过 any_instance）存根类方法。我的测试成功运行，但在测试结束时，当 rspec 尝试重置 any_instance 存根时，它会引发错误（无法从回溯中找到匹配的行）。这是明显的罪魁祸首代码行（删除它会消除错误）：
Confetti::Config.any_instance.stub(:write_info)
完整的错误如下。似乎存根应该（但未能）创建 __rspec_original_dup 方法，并且当重置发生时，它找不到预期的方法。
Failure/Error: Unable to find matching line from backtrace
NameError:
undefined method `__rspec_original_dup' for class `Confetti::Config'
# /Library/Ruby/Gems/1.8/gems/rspec-mocks-2.11.1/lib/rspec/mocks/any_instance.rb:73:in `alias_method'
# /Library/Ruby/Gems/1.8/gems/rspec-mocks-2.11.1/lib/rspec/mocks/any_instance.rb:73:in `restore_dup'
# /Library/Ruby/Gems/1.8/gems/rspec-mocks-2.11.1/lib/rspec/mocks/any_instance.rb:72:in `class_eval'
# /Library/Ruby/Gems/1.8/gems/rspec-mocks-2.11.1/lib/rspec/mocks/any_instance.rb:72:in `restore_dup'
# /Library/Ruby/Gems/1.8/gems/rspec-mocks-2.11.1/lib/rspec/mocks/any_instance.rb:46:in `rspec_reset'
# /Library/Ruby/Gems/1.8/gems/rspec-mocks-2.11.1/lib/rspec/mocks/space.rb:17:in `reset_all'
# /Library/Ruby/Gems/1.8/gems/rspec-mocks-2.11.1/lib/rspec/mocks/space.rb:16:in `each'
# /Library/Ruby/Gems/1.8/gems/rspec-mocks-2.11.1/lib/rspec/mocks/space.rb:16:in `reset_all'
# /Library/Ruby/Gems/1.8/gems/rspec-mocks-2.11.1/lib/rspec/mocks.rb:23:in `teardown'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/mocking/with_rspec.rb:18:in `teardown_mocks_for_rspec'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/example.rb:308:in `run_after_each'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/example.rb:119:in `run'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/example.rb:253:in `with_around_each_hooks'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/example.rb:110:in `run'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/example_group.rb:378:in `run_examples'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/example_group.rb:374:in `map'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/example_group.rb:374:in `run_examples'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/example_group.rb:360:in `run'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/example_group.rb:361:in `run'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/example_group.rb:361:in `map'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/example_group.rb:361:in `run'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/command_line.rb:28:in `run'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/command_line.rb:28:in `map'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/command_line.rb:28:in `run'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/reporter.rb:34:in `report'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/command_line.rb:25:in `run'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/runner.rb:69:in `run'
# /Library/Ruby/Gems/1.8/gems/rspec-core-2.11.1/lib/rspec/core/runner.rb:8:in `autorun'
# /usr/bin/rspec:19