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I'm retrofitting a bunch of existing Hadoop unit tests that were previously run in an in-memory cluster (Using MiniMRCluster) into MRUnit. The existing test cases essentially provide input to the Map phase and then test the output from the Reduce phase.
I have three questions, and the best answer to any of them will qualify:
1) What do I lose, architecturally, by unit testing with MRUnit instead of an in-memory cluster?
2) Is it worthwhile to break the existing test cases up into Map-only tests and Reduce-only tests or not? Are there any cases where I would have to break them up?
3) Are there any testing scenarios that MRUnit is unable to cover?