Starting with ETL unit testing

[TG-SAG]

Hi,
I'm currently trying to get more involved into the development of ETL.
First I cloned it to my linux machine which has g++ (GCC) 8.5.0 20210514 (Red Hat 8.5.0-10) and I got warnings that are errors and I could not compile. For example: -Wunused-variable.
How I generated the tests with run-tests.sh

 Running tests                        
 Configuration   : Initializer list test
 Compiler        : g++ (GCC) 8.5.0 20210514 (Red Hat 8.5.0-10)          
 Language        : C++17   
 Optimisation    : -O2               
 Sanitizer       : Off          
 Compiler select : gcc  
 ETL version     : 20.43.4       
 Git branch      : master  
 Processes       : 4

I then moved to a Github codespace which has the following configuration:

 Running tests                        
 Configuration   : STL
 Compiler        : g++ (Debian 12.2.0-14+deb12u1) 12.2.0          
 Language        : C++17   
 Optimisation    : -O2               
 Sanitizer       : Off          
 Compiler select : gcc  
 ETL version     : 20.43.4       
 Git branch      : master  
 Processes       : 4

But I also got compilation errors:

[ 52%] Building CXX object CMakeFiles/etl_tests.dir/test_fsm.cpp.o
In function ‘void UnitTest::ExecuteTest(T&, const TestDetails&, bool) [with T = {anonymous}::Suitetest_forward_list::SetupFixturetest_sort_emptyHelper]’:
cc1plus: error: potential null pointer dereference [-Werror=null-dereference]
cc1plus: error: potential null pointer dereference [-Werror=null-dereference]

• Is there a list of (GCC) compilers that can compile the ETL unit tests?
• There is a statistic on the https://github.com/ETLCPP/etl that compilations with different compilers and C++ standards are passing. Can I find out (or does anyone know) which compiler versions are used?
• At the end I want to have an development environment that will compile the unit tests.
• Perhaps there are some tips and tricks from other ETL developers on how they compile unit tests. I don't think that it makes sense to delete "-Werror" from the build because it's there for a reason.