This is not how C works

[mateoconlechuga]

By having variables and code in a header file, every time that header is included in a different file, a separate function and variable is created. No one should touch this library as is unless they want to stare at endless linker issues and broken code.

[crowja]

In its place, tinytest.h has been very helpful for me.

[mateoconlechuga]

Ok? That is irrelevant. I'm not saying that it isn't useful, I'm saying that the source code is horrendous. You cannot take a .c file, give it a .h extension, and call it a "single header library" -- not only does this violate the very premise of how C works, it leads to issues that people may not be aware of. Declaring functions and variables in a header file does not protect against multiple compiler invocations, and header guards do not prevent this either.