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From: Andrew Wang <andrew.wang@cloudera.com>
Date: Fri, 29 Sep 2017 13:54:39 -0700
Message-ID: <CAGB5D2Y12gt9akGvg=_DW2Fd+oxbyzUZ17oFKPnQarXtQajCdg@mail.gmail.com>
Subject: Re: [DISCUSS] HADOOP-9122 Add power mock library for writing better
 unit tests
To: Chris Douglas <cdouglas@apache.org>
Cc: Eric Yang <eyang@hortonworks.com>,
	"common-dev@hadoop.apache.org" <common-dev@hadoop.apache.org>
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archived-at: Fri, 29 Sep 2017 20:55:07 -0000

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Making code testable is about a lot more than your mocking library. In
HDFS, the NameNode is very monolithic, so it's hard to instantiate little
pieces of functionality in isolation and mock things out. I have my doubts
that Powermock will help with this unless someone's willing to invest in
significant refactoring effort of our existing code and unit test suites.

I could see an argument of this being useful for new code being developed,
but like Chris, I'd like to see an example of where Mockito falls short,
and what additional capabilities Powermock brings to the table.

Best,
Andrew

On Fri, Sep 29, 2017 at 10:38 AM, Chris Douglas <cdouglas@apache.org> wrote:

> Eric-
>
> Can you explain how Powermock differs from/augments Mockito, why we
> should adopt it, and maybe an example of an existing test that could
> be improved using this library? -C
>
> On Fri, Sep 29, 2017 at 10:12 AM, Eric Yang <eyang@hortonworks.com> wrote:
> > Hi Hadoop-dev,
> >
> > Long time ago, Hadoop community decided to put Powermock on hold for
> unit tests.  Both mockito and powermock has evolved a lot in the past 5
> years.  There are mature versions of both software, and there are
> compatibility charts to indicate which versions can work together.  Hadoop
> has grown a lot in the last 5 years.  It becomes apparent that without
> ability to instrument lower level classes to contain unit test scope.  Many
> tests are written to simulate integration test in order to perform unit
> tests.  The result is slow performance on unit tests, and some parts are
> not testable strictly in unit test case.  This discussion is to revisit the
> decision, and see if we would embrace Powermock and allow HADOOP-9122 to be
> implemented.  Feel free to comment on HADOOP-9122 and this thread to
> revisit this issue.
> >
> > Thank you for your time.
> >
> > Regards,
> > Eric
>
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