Tests of Fleur and its features

There are always not enough tests. Collect tests requests here, especially for features.

(the test system might be adapted to which libraries Fleur was compiled with)

So far there is no test for (correct me if I am wrong):

1. with HDF5 (should not be tested if compiled without)

2. General other external dependencies/libraries (LAPACK, ELPA, MAGMA, compilers?). We should somehow know if some changes in these 'break'/change something. I do not know what are sensible tests here. (Maybe for a 'general' check just run all the usual tests for different libraries linked in) Also that we can just tell users, not use this or this version.

3. Usability with AiiDA (so far I do not see a good way of doing this)

4. Out.xml schema: if the out.xml file applies to the schema? (if we do not test it there is no point in having one, because other tools can not rely on it) We should know if a commit breaks it, or if it has to be adapted.

...