This test scenario is for a distributed cache file behaviour
when it is not modified before and after being
accessed by maximum two jobs. Once a job uses a distributed cache file
that file is stored in the mapred.local.dir. If the next job
uses the same file, then that is not stored again.
So, if two jobs choose the same tasktracker for their job execution
then, the distributed cache file should not be found twice.
This testcase should run a job with a distributed cache file. All the
tasks' corresponding tasktracker's handle is got and checked for
the presence of distributed cache with proper permissions in the
proper directory. Next when job
runs again and if any of its tasks hits the same tasktracker, which
ran one of the task of the previous job, then that
file should not be uploaded again and task use the old file.