Why does writing write () with stdin lead to exit?

Question

I can understand why the entry in stdout and stderr will be output, but why stdin?

#include <unistd.h>

int
main()
{
  const char test[] = "test test test\n";
  write(STDIN_FILENO, test, sizeof(test) - 1);
  return 0;
}

EDIT: for those who want to try, you can compile and run the program here