The AppEngine-Pipelines library has some restrictions about what can be yielded from CrashWrapperPipeline.run (e.g., what arguments the yielded objects' run method accepts). The current unittests mock out CrashWrapperPipeline.run, so while they work for testing the run methods on the other pipelines, they fail to catch this issue about yield. The mocking should be made more robust so that it captures this issue as well