tests/fmt/tests_for_usage.c

#include "../../unity/unity.h"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>

/* Unity hooks */
void setUp(void) {
  /* No setup needed */
}
void tearDown(void) {
  /* No teardown needed */
}

/* Helper to read all data from an fd into a NUL-terminated buffer.
   The returned buffer must be free()'d by the caller. */
static char* read_all_from_fd(int fd, size_t *out_len) {
  size_t cap = 4096;
  size_t len = 0;
  char *buf = (char*)malloc(cap);
  if (!buf) return NULL;

  for (;;) {
    if (len + 2048 > cap) {
      size_t new_cap = cap * 2;
      char *nb = (char*)realloc(buf, new_cap);
      if (!nb) {
        free(buf);
        return NULL;
      }
      buf = nb;
      cap = new_cap;
    }
    ssize_t n = read(fd, buf + len, cap - len - 1);
    if (n < 0) {
      if (errno == EINTR) continue;
      free(buf);
      return NULL;
    }
    if (n == 0) break;
    len += (size_t)n;
  }
  buf[len] = '\0';
  if (out_len) *out_len = len;
  return buf;
}

/* Run usage(status) in a child process, capturing stdout/stderr and exit code. */
struct usage_run_result {
  int exit_code;      /* child exit status (0-255 if exited normally, else 128+signal) */
  char *out_buf;      /* captured stdout (malloc'd) */
  size_t out_len;
  char *err_buf;      /* captured stderr (malloc'd) */
  size_t err_len;
  int ok;             /* 1 on success, 0 on setup error */
};

static struct usage_run_result run_usage_and_capture(int status_code) {
  struct usage_run_result res;
  memset(&res, 0, sizeof(res));
  res.exit_code = -1;
  res.ok = 0;

  int out_pipe[2] = {-1, -1};
  int err_pipe[2] = {-1, -1};
  if (pipe(out_pipe) != 0) return res;
  if (pipe(err_pipe) != 0) { close(out_pipe[0]); close(out_pipe[1]); return res; }

  fflush(stdout);
    fflush(stderr);
    pid_t pid = fork();
  if (pid < 0) {
    close(out_pipe[0]); close(out_pipe[1]);
    close(err_pipe[0]); close(err_pipe[1]);
    return res;
  }

  if (pid == 0) {
    /* Child: redirect stdout/stderr and call usage */
    /* Close read ends */
    (void)close(out_pipe[0]);
    (void)close(err_pipe[0]);

    /* Redirect stdout/stderr */
    (void)dup2(out_pipe[1], STDOUT_FILENO);
    (void)dup2(err_pipe[1], STDERR_FILENO);

    /* Close the duplicated write ends */
    (void)close(out_pipe[1]);
    (void)close(err_pipe[1]);

    /* Call the function under test; it should exit(). */
    usage(status_code);

    /* If it returns unexpectedly, exit with a distinctive code. */
    _exit(127);
  }

  /* Parent */
  (void)close(out_pipe[1]);
  (void)close(err_pipe[1]);

  /* Read all output */
  res.out_buf = read_all_from_fd(out_pipe[0], &res.out_len);
  res.err_buf = read_all_from_fd(err_pipe[0], &res.err_len);
  (void)close(out_pipe[0]);
  (void)close(err_pipe[0]);

  int wstatus = 0;
  pid_t w = waitpid(pid, &wstatus, 0);
  if (w < 0) {
    /* wait failed */
    res.ok = 0;
    return res;
  }

  if (WIFEXITED(wstatus)) {
    res.exit_code = WEXITSTATUS(wstatus);
  } else if (WIFSIGNALED(wstatus)) {
    res.exit_code = 128 + WTERMSIG(wstatus);
  } else {
    res.exit_code = -2; /* unknown */
  }
  res.ok = 1;
  return res;
}

/* Tests */

static void free_usage_result(struct usage_run_result *r) {
  if (!r) return;
  free(r->out_buf);
  free(r->err_buf);
  r->out_buf = NULL;
  r->err_buf = NULL;
}

void test_usage_success_exits_zero_and_writes_to_stdout(void) {
  struct usage_run_result r = run_usage_and_capture(EXIT_SUCCESS);
  TEST_ASSERT_MESSAGE(r.ok, "Failed to set up or run usage()");
  TEST_ASSERT_EQUAL_INT_MESSAGE(0, r.exit_code, "usage(EXIT_SUCCESS) should exit with status 0");
  /* Expect some help/usage text on stdout */
  TEST_ASSERT_TRUE_MESSAGE(r.out_len > 0, "Expected non-empty stdout for EXIT_SUCCESS");
  /* We don't assert on stderr content due to localization; it may contain ancillary notes */
  free_usage_result(&r);
}

void test_usage_failure_exits_failure_and_writes_try_help_to_stderr(void) {
  struct usage_run_result r = run_usage_and_capture(EXIT_FAILURE);
  TEST_ASSERT_MESSAGE(r.ok, "Failed to set up or run usage()");
  TEST_ASSERT_EQUAL_INT_MESSAGE(EXIT_FAILURE, r.exit_code, "usage(EXIT_FAILURE) should exit with EXIT_FAILURE");
  /* For failure, usage() is expected to not print the full usage to stdout. */
  TEST_ASSERT_TRUE_MESSAGE(r.out_len == 0, "Expected empty stdout for non-success status");
  /* Help hint should go to stderr; assert non-empty */
  TEST_ASSERT_TRUE_MESSAGE(r.err_len > 0, "Expected non-empty stderr for non-success status");
  free_usage_result(&r);
}

int main(void) {
  UNITY_BEGIN();
  RUN_TEST(test_usage_success_exits_zero_and_writes_to_stdout);
  RUN_TEST(test_usage_failure_exits_failure_and_writes_try_help_to_stderr);
  return UNITY_END();
}