[Qt-creator] Unit testing private parts of shared libraries

[Elvis Stansvik]

Hi all,

(Posting this as a new thread instead of necroposting to my old thread
about the design of Qt Creator [1], which did end with some
discussions about testing.)

I'm working on some tests for my own application, and started thinking
about unit testing of private parts of shared libraries (think the
_p.h/_p.cpp parts). Such parts are normally not exported AFAIK (in the
visibility attribute sense). This becomes a problem if you link the
unit tests dynamically against the code under test, as the tests won't
be able to see those symbols.

So it seems to me there is only a few options:

 1. Exporting the private parts after all,
 2. Adding the sources of the code under test to the unit tests,
 3. ?

1 is not really good, as you export more than you really have to. But
I guess it's not so bad after all, since you a) have to include _p.h
to get at them and b) they're normally called PrivateSomething or
InternalSomething, both of which should tell you you're doing
something bad. 2 is not really good either though, as you really want
to test the code as shipped, not as compiled as part of your test.

I had a quick look at Qt Creator because I know you folks are seasoned
developers, and it looks like you've gone with option 1. For example,
ExtensionSystem::Internal::PluginSpecPrivate is exported, and I guess
the reason is you want to be able to unit test it?

I just wanted to ask in case you have any other ideas or better ways
to let unit tests access things that are normally not exported?

Thanks in advance,
Elvis

[1] http://lists.qt-project.org/pipermail/qt-creator/2017-September/006712.html