[GNC-dev] Rework GoogleTest integration

[John Ralls]

> On Aug 15, 2019, at 3:22 PM, Christian Gruber <christian.gruber at posteo.de> wrote:
> 
> Am 15.08.19 um 00:23 schrieb Christian Gruber:
>> 
>>> I think our distro packagers would object to any option other than relying on tools outside of the build system to provide the googletest sources and maybe a prebuilt static lib. It's a one-off for the casual builder and easily scripted for everyone else. Building gtest is also sufficiently trivial that it's not all that interesting to call out to guests own CMakeLists.txt instead of just building the two libraries in ours. OTOH it's possible that might change at some point, so
>> 
>> Ok, so you want to keep build process as it is at the moment. In this case at least bug 797344 should be fixed. I'll provide a PR. And I recommend to use library target gtest directly instead of variables GTEST_LIB, GTEST_INCLUDE_DIR as stated above. The same I recommend for library target gmock. I'll add this to the same PR.
>> 
>> Finally I recommend to add a few more notes on the Wiki page https://wiki.gnucash.org/wiki/Google_Test. For me not familiar with the GnuCash build system it was not obvious at the beginning, that gtest is built inside GnuCash build system, because this is a little bit unusual. It could for instance be explained, how to build gtest and gmock from inside GnuCash build system via "make gtest" and "make gmock" and that this way one can test the correct CMake configuration for GnuCash regarding variables GTEST_ROOT and GMOCK_ROOT. The Wiki page only explains how to "test the installation" from inside the GoogleTest build system and tells that this is "not used in practice". But this doesn't really test the CMake configuration for GnuCash.
>> 
>>> 
>>> I don't think anyone's actually tried doing a mock with GMock yet. There are hand-rolled ones in the QOF tests, but they use the old Glib test facility. Most of the C++ work so far has been at the lowest levels so that the C++ classes don't have any mockable dependencies. That will change when we get to redoing the engine as we'll want to use mock for at least the backend. We don't want to remove GMock from the dependencies.
>>> 
>>> I agree about libgtest_main.a. Would you like to make a PR to remove all of the inclusion of gtest_main.cc and GTEST_SRC?
>> I opened PR https://github.com/Gnucash/gnucash/pull/552.
>>> 
>>> Regards,
>>> John Ralls
>>> 
>> Regards,
>> Christian
>> 
> I just realized now, after PR https://github.com/Gnucash/gnucash/pull/552 failed to build, that there is a significant difference between using prebuilt GoogleTest libraries and building GoogleTest from source repository. In the latter case libgtest_main.a doesn't exist at all, it isn't built anywhere. And GTEST_LIB contains only libgtest.a in this case. Therefore I created a new pull request https://github.com/Gnucash/gnucash/pull/555, which removes GTEST_SRC and additionally adds source file gtest_main.cc to the sources of libgtest.a. I also thought about creating a second target gtest_main for building libgtest_main.a as in GoogleTest source repository, but in the end I thought that's exaggerated, because both libraries are always used in combination in GnuCash.

That's fine, and I've merged your PR.

Regards,
John Ralls