libc tests based on libc-testsuit by Rich Felker
see http://git.musl-libc.org/cgit

configure tests:
	cp dist/config.mak .
	# edit config.mak
build tests:
	make
run tests:
	make run

design goals:

- tests should be easy to run even a single test in isolation
(so test should be self contained if possible)
- failure of one test should not interfere with others
(build failure, crash or unexpected results are all failures)
- test output should point to the cause of failure
- test results should be robust
- the test system should have minimal dependency
(libc, posix sh, gnu make)
- the test system should run on all archs and libcs
- tests should leave the system in a clean state

framework:

the convention is that each test is in a separate file
at a path like src/directory/file.c with its own main

the test should return 0 on success and non-0 on failure
error messages relevant to the test system should be
printed to standard out (fd 1)

src/functional/test.h usage:

use error in tests when possible instead of printf
(error truncates the formatted string to 512 bytes and uses a
single write call to output it to fd 1, terminating the error
string with a \n is the responsibility of the caller)
and return test_status from main (set by error, 0 by default)

when many similar checks are done, helper macros can be used like
#define T1(a,b) (check(a,b) || (error("check(%s,%s) failed\n", a, b),0))
#define T2(f,w) (result=(f), result==(w) || (error("%s failed: got %s, want %s\n", #f, result, w),0))

a simple example:

#include "test.h"
#define T(c,...) ((c) || (error(#c " failed: " __VA_ARGS__),0))
int main(void)
{
	T('a'+1=='b', "'a'==%d 'b'==%d\n", 'a', 'b');
	T(-5%3==-2, "bad mod semantics\n");
	return test_status;
}