feat(system/esp_stdio): Add test coverage for esp_stdio refactor

components/esp_stdio/test_apps/stdio/main/test_app_main.c

@@ -1,11 +1,12 @@
 /*
- * SPDX-FileCopyrightText: 2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2024-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
 #include <stdio.h>
 #include <assert.h>
 #include <string.h>
+#include <errno.h>
 #include "sdkconfig.h"
 
 #include "esp_rom_serial_output.h"
@@ -50,6 +51,7 @@ static void console_none_print(void)
 #endif
 
 #if CONFIG_VFS_SUPPORT_IO
+#if CONFIG_ESP_STDIO_MAX_FDS <= 0 || CONFIG_ESP_STDIO_MAX_FDS > 3
 static void console_open_close_check(void)
 {
     printf("Opening /dev/console\n");
@@ -65,6 +67,110 @@ static void console_open_close_check(void)
 
     printf("This should be printed to stdout\n");
 }
+#endif
+
+static void stdio_fd_mode_behavior_check(void)
+{
+#if CONFIG_ESP_STDIO_MAX_FDS <= 0
+    printf("STDIO_TEST:MODE=BASIC\n");
+
+    int fd0 = open("/dev/console", O_RDWR);
+    int fd1 = open("/dev/console", O_RDWR);
+    int fd2 = open("/dev/console", O_RDWR);
+    assert(fd0 >= 0);
+    assert(fd1 >= 0);
+    assert(fd2 >= 0);
+    printf("STDIO_TEST:BASIC:OPEN_OK\n");
+
+    const char *msg = "STDIO_TEST:BASIC:WRITE_OK\n";
+    ssize_t wr = write(fd0, msg, strlen(msg));
+    assert(wr == (ssize_t) strlen(msg));
+
+    assert(close(fd0) == 0);
+    assert(close(fd1) == 0);
+    assert(close(fd2) == 0);
+    printf("STDIO_TEST:BASIC:CLOSE_OK\n");
+
+    errno = 0;
+    assert(close(-1) < 0);
+    assert(errno == EBADF);
+
+    errno = 0;
+    assert(write(fd0, msg, strlen(msg)) < 0);
+    assert(errno == EBADF);
+    printf("STDIO_TEST:BASIC:EBADF_OK\n");
+#else
+    printf("STDIO_TEST:MODE=NON_BASIC\n");
+
+    errno = 0;
+    int fd0 = open("/dev/console", O_RDWR);
+    if (fd0 < 0) {
+        /* Small fd limits can be fully consumed by stdin/stdout/stderr. */
+        assert(errno == ENFILE);
+        printf("STDIO_TEST:NON_BASIC:SATURATED_OK\n");
+        return;
+    }
+
+    int fd1 = open("/dev/console", O_RDWR);
+    int fd2 = open("/dev/console", O_RDWR);
+    assert(fd0 >= 0);
+    assert(fd1 >= 0);
+    assert(fd2 >= 0);
+    assert(fd0 != fd1 && fd1 != fd2 && fd0 != fd2);
+    printf("STDIO_TEST:NON_BASIC:UNIQUE_OK\n");
+
+    assert(close(fd1) == 0);
+    int fd_reused = open("/dev/console", O_RDWR);
+    assert(fd_reused == fd1);
+    printf("STDIO_TEST:NON_BASIC:REUSE_OK\n");
+    assert(close(fd0) == 0);
+    assert(close(fd2) == 0);
+    assert(close(fd_reused) == 0);
+
+    int fds[CONFIG_ESP_STDIO_MAX_FDS + 2];
+    int opened = 0;
+    while (opened < (int)(sizeof(fds) / sizeof(fds[0]))) {
+        int fd = open("/dev/console", O_RDWR);
+        if (fd < 0) {
+            break;
+        }
+        fds[opened++] = fd;
+    }
+    assert(opened >= 0);
+    assert(opened <= CONFIG_ESP_STDIO_MAX_FDS);
+    errno = 0;
+    assert(open("/dev/console", O_RDWR) < 0);
+    assert(errno == ENFILE);
+    printf("STDIO_TEST:NON_BASIC:LIMIT_OK\n");
+
+    for (int i = 0; i < opened; ++i) {
+        assert(close(fds[i]) == 0);
+    }
+
+    const char *msg = "x";
+    errno = 0;
+    assert(write(-1, msg, 1) < 0);
+    assert(errno == EBADF);
+    printf("STDIO_TEST:NON_BASIC:EBADF_OK\n");
+#endif
+}
+
+static void stdio_fd_init_check(void)
+{
+    int in_fd = fileno(stdin);
+    int out_fd = fileno(stdout);
+    int err_fd = fileno(stderr);
+
+    assert(in_fd == 0);
+    assert(out_fd == 1);
+    assert(err_fd == 2);
+
+    printf("STDIO_TEST:FD_INIT:IN=%d,OUT=%d,ERR=%d\n", in_fd, out_fd, err_fd);
+    fprintf(stdout, "STDIO_TEST:STREAM:STDOUT\n");
+    fflush(stdout);
+    fprintf(stderr, "STDIO_TEST:STREAM:STDERR\n");
+    fflush(stderr);
+}
 #endif // CONFIG_VFS_SUPPORT_IO
 
 void app_main(void)
@@ -80,6 +186,8 @@ void app_main(void)
     assert(fd > 2 && "Incorrect file descriptor returned, stdin, stdout, stderr were not correctly assigned");
 
     close(fd);
+
+    stdio_fd_init_check();
 #endif // CONFIG_VFS_SUPPORT_IO
 
 #if CONFIG_ESP_CONSOLE_NONE
@@ -87,7 +195,12 @@ void app_main(void)
 #endif // CONFIG_ESP_CONSOLE_NONE
 
 #if CONFIG_VFS_SUPPORT_IO
+#if CONFIG_ESP_STDIO_MAX_FDS <= 0 || CONFIG_ESP_STDIO_MAX_FDS > 3
     console_open_close_check();
+#else
+    printf("STDIO_TEST:SKIP:OPEN_CLOSE_CHECK\n");
+#endif
+    stdio_fd_mode_behavior_check();
 #endif // CONFIG_VFS_SUPPORT_IO
 
 }