I want to thank Jesse for taking up this issue considering he has been busy with other big feature(s).
I would say let's try a few examples after which the benefit of introducing powermock would be clearer. Cheers On Fri, Sep 14, 2012 at 7:16 PM, Jesse Yates <jesse.k.ya...@gmail.com>wrote: > Hi all, > > TL;DR powermock is really hard (and ugly) to get working for the > class-loading abilities, but has a really nice reflection library we can > leverage. To get the low-level access we could instead use jmockit at the > cost of dealing with code-weaving. > > At the pow-wow there was also some discussion of ways in which we can > improve the testing infrastructure. Options toss around were things like > improving the testing util, fixing classes to make them more testable, and > powermock. > > The first two are definitely the right way to go, but can be pretty hard to > do (problem with all legacy code) and often times can lead to awkward code > to facilitate testing. Here, PowerMock is great - it lets you get into the > internals more easily. > > That said, I've started working on HBASE-5456 (Introduce PowerMock into our > unit tests to reduce unnecessary method exposure) and its a hairy mess. > Powermock's whole functionality is based on using its own classloader. > However, because of all the reflection that HBase and Hadoop does > (particularly Hadoop here), we end up having to do a ton of ignore > statements for classes/packages that PowerMock shouldn't load. I hacked on > it for a bit and still couldn't get a mini-cluster up and running :-/ > > Even given that pain we can get a lot of use from the reflection utilities > - this allows you to replace existing objects with mocks, access private > methods (no more 'exposed for testing methods'). The powermock jars amount > to about 100K - small overhead for a lot the helper methods. See > http://code.google.com/p/powermock/wiki/BypassEncapsulation > > To resolve the cases where the powermock class-loading would be useful > (e.g. catching object creation to use your own mock, rather than using > factories or DI everywhere) we could use jmockit. Jmockit does the same > basic stuff as powermock (minus the nice reflection library), but it does > it through run-time code weaving for tests through the java agent > framework. > > This will give us really fine grained access to the code under test without > having to do a lot of funky rewrites. However, code-weaving comes at the > cost of loosing debugger usage as the code-weaving messes with the > bytecode. I'd argue that its a small price to pay for getting highly > controllable tests, *as long as we don't go overboard with the > weaving.*Yes, when we start doing too much test weaving it can become > untenable, but > it can be really useful for many situations without having to write > funky/awkward code. > > What do ya'll think? > > Thanks, > Jesse > ------------------- > Jesse Yates > @jesse_yates > jyates.github.com >
