It is. Thank you!

C: Tests don't run.

How to reproduce: Just reset the solution and click on "Attempt".

STDERR:

/tmp/fixture-d19c8e.o: In function `test_cases_random_tests_impl':
fixture.c:(.text+0xd4f): undefined reference to `format'
fixture.c:(.text+0xd75): undefined reference to `format'
fixture.c:(.text+0xd93): undefined reference to `format'
fixture.c:(.text+0xdb6): undefined reference to `format'
fixture.c:(.text+0xdd7): undefined reference to `format'
/tmp/fixture-d19c8e.o:fixture.c:(.text+0xdfa): more undefined references to `format' follow
clang: error: linker command failed with exit code 1 (use -v to see invocation)