Welcome to flase, yes its spelled correctly. The library name is an ode to how I used to misspell false ... and still do sometimes. This is meant to be a super simple macro library for writing and running tests in C.

It's really simple, all you have to do is #include "flase.h" and define your test cases. There are really only three macro functions you'll need FLASE_DEFINE_TEST, FLASE_ASSERT and FLASE_RUN_TEST. These define tests, add asserts to the tests scope and run the specified test respectively. Below is a simple example and the output.

// sample.c
#include "flase.h"

FLASE_DEFINE_TEST( simple )
{
	FLASE_ASSERT( 1 == 0, "Whoopsie" );
	FLASE_ASSERT( 1 == 1, "This must be true" );
}

FLASE_DEFINE_TEST( apples )
{
	FLASE_ASSERT( 1 < 2, "Correcto" );
	FLASE_ASSERT( 2 > 1, "Yes" );
}

int main()
{
	FLASE_RUN_TEST( simple );
	FLASE_RUN_TEST( apples );

	return 0;
} 

Building sample.c and running it we get the following output: (with nice color printing which I unfortunately can't show here)

FLASE Run Test: simple
	Failed: Whoopsie, sample.c:5
FLASE Error Report: simple | FAIL [1/2]
FLASE Run Test: apples | PASS [2/2]

If you really don't want to use the standard library you'll need to provide an alternate definition for the print function that flase uses. You can do this by defining FLASE_PRINT to be the name of a function that satisfies the interface of printf.

This is the interface: int printf(const char* restrict format, ...);

I would suggest externing your custom_printf function from whatever C file you implement it in before you include the flase header. After the extern, add #define FLASE_PRINT custom_printf to tell flase what print function to use, and then include the flase header.

I would create one header for each regular header file from your program. Each test header can then test all of the functions / machinary that is laid out in that program header. So for example if you had a math.h file I would create a tests_math.h test file. I would then include the flase header, math.h along with whatever other headers you might need. After that, I would define all your test functions, and potentially a function to call FLASE_RUN_TEST for all of the tests you defined for the header file you are testing.

In your test application entry point file, I would include all of your test headers including test_math.h. You can then call your tests individually using FLASE_RUN_TEST or call the function you've created that runs all the tests from each header.

If you don't want to use stdc, I would define FLASE_PRINT before including any of your test headers in the entry point file.

If you are using a tool like cmake, I would recommend building a separate test target.