void assert_within(uint16_t expected, uint16_t actual, uint16_t tolerance, const char* text)
{
    char buf[64];
    if(abs(expected-actual) > tolerance) {
        snprintf(buf, ARRAY_SIZE(buf), "%s outside tolerance, expected within %d of %d, got %d", text, tolerance, expected, actual);
        FAIL_TEXT_C(buf);
    }
}