Unit tests in C

hello.c

#include <stdio.h>
#include "hello.h"
#include "log.h"

void hello() {
  for (int i = 0; i < 10; i++) {
    log_printf("Hello, world!\n");
  }
}

hello.h

#ifndef _HELLO_H
#define _HELLO_H

void hello();

#endif

log.c

#include <stdio.h>

void log_printf(char* message) {
  printf("%s", message);
}

log.h

#ifndef _LOG_H
#define _LOG_H

void log_printf(char* message);

#endif

main.c

#include "hello.h"

int main() {
  hello();
  return 0;
}

run.sh

gcc main.c hello.c log.c -o main.o && ./main.o

test.c

#include <stdio.h>
#include <strings.h>
#include "hello.h"
#include "log.h"

static char* last_message = 0;
static int calls = 0;

void log_printf(char* message) {
  calls++;
  last_message = message;
}

int main() {
  hello();

  if (strcmp(last_message, "Hello, world!\n") != 0) {
    return 1;
  }

  if (calls != 10) {
    return 2;
  }

  return 0;
}

test.sh

gcc test.c hello.c -o test.o && ./test.o