C 如何为另一个使用标准输入的函数编写测试函数？

作为大学任务的一部分，我具有以下职能：

int readMenuOption()
{
   /* local declarations */
   char option[2];
   /* read in 1 char from stdin plus 1 char for string termination character */
   readStdin(1 + 1, option);
   return (int)option[0] <= ASCII_OFFSET ? 0 : (int)option[0] - ASCII_OFFSET;
}

int readStdin(int limit, char *buffer) 
{
   char c;
   int i = 0;
   int read = FALSE;
   while ((c = fgetc(stdin)) != '\n') {
      /* if the input string buffer has already reached it maximum
       limit, then abandon any other excess characters. */
      if (i <= limit) {
         *(buffer + i) = c;
         i++;
         read = TRUE;
      }
   }
   /* clear the remaining elements of the input buffer with a null character. */
   for (i = i; i < strlen(buffer); i++) {
      *(buffer + i) = '\0';
   }
   return read;
}

int readMenuOption（）
{
/*本地声明*/
字符选项[2]；
/*从stdin读入1个字符加上1个字符作为字符串终止字符*/
readStdin（1+1，可选）；
返回（int）选项[0]查找非标准但非常有用的函数。然后执行以下操作：

int ptyfd;
pid = forkpty(&ptyfd, 0, 0, 0);
if (pid<0) perror("forkpty"), exit(1);
if (!pid) {
    /* call your function to be tested */
    _exit(1);
} else {
    /* write to ptyfd here to generate input for the function */
}

char *fakeStdIn = "";
int myfgetc (FILE *fin) {
    if (*fakeStdIn == '\0')
        return fgetc (fin);
    return *fakeStdIn++;
}

int readStdin(int limit, char *buffer) 
{
   char c;
   int i = 0;
   int read = FALSE;
   while ((c = myfgetc(stdin)) != '\n') {
      /* if the input string buffer has already reached it maximum
       limit, then abandon any other excess characters. */
      if (i <= limit) {
         *(buffer + i) = c;
         i++;
         read = TRUE;
      }
   }
   /* clear the remaining elements of the input buffer with a null character. */
   for (i = i; i < strlen(buffer); i++) {
      *(buffer + i) = '\0';
   }
   return read;
}

./a.out < input.txt

intptyfd；
pid=forkpty（&ptyfd，0,0,0）；
如果（pid您可以做的一件事是简单地修改
readStdin
，以允许它从实际的标准输入或辅助函数获取数据，例如：

int ptyfd;
pid = forkpty(&ptyfd, 0, 0, 0);
if (pid<0) perror("forkpty"), exit(1);
if (!pid) {
    /* call your function to be tested */
    _exit(1);
} else {
    /* write to ptyfd here to generate input for the function */
}

char *fakeStdIn = "";
int myfgetc (FILE *fin) {
    if (*fakeStdIn == '\0')
        return fgetc (fin);
    return *fakeStdIn++;
}

int readStdin(int limit, char *buffer) 
{
   char c;
   int i = 0;
   int read = FALSE;
   while ((c = myfgetc(stdin)) != '\n') {
      /* if the input string buffer has already reached it maximum
       limit, then abandon any other excess characters. */
      if (i <= limit) {
         *(buffer + i) = c;
         i++;
         read = TRUE;
      }
   }
   /* clear the remaining elements of the input buffer with a null character. */
   for (i = i; i < strlen(buffer); i++) {
      *(buffer + i) = '\0';
   }
   return read;
}

./a.out < input.txt

通过将钩子放在较低的级别，您可以注入自己的字符序列，而不是使用标准输入。如果在任何时候，伪标准输入耗尽，它将恢复为真实输入

显然，这是在使用字符，因此，如果要注入EOF事件，则需要一个整数数组，但这只是对方案的一个小修改。
为什么不能使用重定向？类似于：

int ptyfd;
pid = forkpty(&ptyfd, 0, 0, 0);
if (pid<0) perror("forkpty"), exit(1);
if (!pid) {
    /* call your function to be tested */
    _exit(1);
} else {
    /* write to ptyfd here to generate input for the function */
}

char *fakeStdIn = "";
int myfgetc (FILE *fin) {
    if (*fakeStdIn == '\0')
        return fgetc (fin);
    return *fakeStdIn++;
}

int readStdin(int limit, char *buffer) 
{
   char c;
   int i = 0;
   int read = FALSE;
   while ((c = myfgetc(stdin)) != '\n') {
      /* if the input string buffer has already reached it maximum
       limit, then abandon any other excess characters. */
      if (i <= limit) {
         *(buffer + i) = c;
         i++;
         read = TRUE;
      }
   }
   /* clear the remaining elements of the input buffer with a null character. */
   for (i = i; i < strlen(buffer); i++) {
      *(buffer + i) = '\0';
   }
   return read;
}

./a.out < input.txt

/a.out

其中“input.txt”将包含您想要给程序的任何输入。
可能重复的