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https://issues.apache.org/jira/browse/MRUNIT-127?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13427571#comment-13427571
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Dave Beech commented on MRUNIT-127:
-----------------------------------
Yep - I've confirmed that the expected outputs of the "testComparators" tests
do not agree with an actual MapReduce run. So, I'll fix these tests and commit
the patch in this morning unless anyone has objections.
> Key grouping with GroupingComparators is not consistent with MapReduce
> behaviour
> --------------------------------------------------------------------------------
>
> Key: MRUNIT-127
> URL: https://issues.apache.org/jira/browse/MRUNIT-127
> Project: MRUnit
> Issue Type: Bug
> Affects Versions: 0.9.0
> Reporter: Dave Beech
> Assignee: Dave Beech
> Fix For: 1.0.0
>
> Attachments: MRUNIT-127.patch
>
>
> In Hadoop MapReduce, for a set of keys to be properly grouped together by a
> grouping comparator into a reduce call, they need to be in a contiguous range
> when sorted by the key's ordering comparator.
> MRUnit does not impose this requirement, so if the user's grouping and
> sorting comparator logic is incorrect, their tests may pass and give the
> expected result even though the outcome would be different when run as a true
> MapReduce job.
> (see below for further explanation)
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