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https://issues.apache.org/jira/browse/HADOOP-9122?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Eric Yang updated HADOOP-9122:
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Resolution: Won't Fix
Assignee: (was: Eric Yang)
Status: Resolved (was: Patch Available)
Mock provides tool chains to run simulation for a piece of code. It helps to
prevent null pointer exception, and reduce unexpected runtime exceptions. When
a piece of code is finished with a well-defined unit test, it provides great
insights to see author’s intention and reasoning to write the code. However,
everyone looks at code from a different perspective, and it is often easier to
rewrite the code than modifying and update the tests. The short coming of
writing new code, there is always danger of losing existing purpose, workaround
buried deep in the code. On the other hand, if a test program is filling with
several pages of initialization code, and override. It is hard to get context
of the test case, and easy to lose the original meaning of the test case.
Hence, there are drawback for using mock or full integration test.
I was in favor of using Powermock in favor of giving user the ability to unit
test a class and reduce external interference initially. However, I quickly
come to realization that Hadoop usage of protocol buffer serialization
technique and java reflection serialization technique have some difference
which prevents powermock to work for certain Hadoop classes.
Hadoop unit tests are written to be bigger than one class, and frequently, a
mini-cluster is spawned to test 5-10 lines of code. Any simple API test will
trigger large portion of Hadoop code to be initialized. Hadoop code base will
require too much effort to work with Powermock. Programs outside of Hadoop can
use powermock annotation to prevent mocking Hadoop classes, such as:
@powermockignore({"javax.management_", "javax.xml.", "org.w3c.",
"org.apache.hadoop._", "com.sun.*"}) . However, working in Hadoop code base,
this technique is not practical because every class in Hadoop prefix with
org.apache.hadoop. It will be heavy upkeep to maintain the list of prefix
packages that can not work with powermock reflection.
Hence, I rest my case for re-opening this issue.
> Add powermock library for writing better unit tests
> ---------------------------------------------------
>
> Key: HADOOP-9122
> URL: https://issues.apache.org/jira/browse/HADOOP-9122
> Project: Hadoop Common
> Issue Type: Improvement
> Reporter: Radim Kolar
> Priority: Critical
> Attachments: HADOOP-9122.001.patch, powermock.txt
>
>
> This library is extension of mockito and easymock libraries. It allows
> testing of private methods, private variables and other otherwise untestable
> stuff.
> http://code.google.com/p/powermock/
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