C API test using google test

[benegee]

First part adressing #73

[codecov]

Codecov Report

Merging #80 (231dc68) into main (e19b886) will increase coverage by 18.81%.
The diff coverage is 100.00%.

❗ Current head 231dc68 differs from pull request most recent head d89194d. Consider uploading reports for the commit d89194d to get more accurate results

@@             Coverage Diff             @@
##             main      #80       +/-   ##
===========================================
+ Coverage   77.07%   95.88%   +18.81%     
===========================================
  Files           8        8               
  Lines         314      316        +2     
===========================================
+ Hits          242      303       +61     
+ Misses         72       13       -59     

Flag	Coverage Δ
unittests	95.88% <100.00%> (+18.81%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
examples/simple_trixi_controller.f90	100.00% <100.00%> (+29.41%)	⬆️
examples/trixi_controller_data.f90	100.00% <100.00%> (+26.31%)	⬆️
src/auxiliary.c	93.87% <100.00%> (+49.19%)	⬆️

... and 3 files with indirect coverage changes

[benegee]

Coverage is rising 🥳

But, I do not know how to provoke this one:

libtrixi/src/auxiliary.c

Lines 116 to 120 in bb9582c

	if (fptrs[i] == NULL) {
	fprintf(stderr, "ERROR: could not get function pointer with `%s()`\n",
	fptr_names[i]);
	print_and_die("null pointer", LOC);
	}

If a non-existing function pointer name is given, the execution of the julia command will already abort with an error message.

[sloede]

If a non-existing function pointer name is given, the execution of the julia command will already abort with an error message.

Yeah, this path you cannot easily check. Just leave it be for now.

[sloede]

Just a few small comments, but otherwise this looks great!

[sloede]

More than 95% coverage 🥳

[sloede]

LGTM! Great work!