[pseudo,3/6] tests: Add test that returned stat is correct

diff --git a/test/test-db-mode.c b/test/test-db-mode.c
new file mode 100644
index 0000000..1e470c2
--- /dev/null
+++ b/test/test-db-mode.c
@@ -0,0 +1,117 @@ 
+/*
+ * Test that PSEUDO_DB_MODE correctly reconstructs permissions at file
+ * creation time. PSEUDO_DB_MODE is used when a file is created (open
+ * with O_CREAT, mkdir, etc.) to recover the intended mode from the
+ * filesystem mode (which has been mangled by PSEUDO_FS_MODE).
+ *
+ * If PSEUDO_DB_MODE is broken, the mode stored in the database at
+ * creation time will be wrong, which we detect by stat'ing immediately
+ * after creation (before any chmod).
+ *
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+static int test_creat_mode(mode_t mode) {
+    const char *path = "test-db-mode-tmp";
+    struct stat st;
+
+    /* Remove any prior file */
+    unlink(path);
+
+    /* Clear umask so it doesn't interfere */
+    mode_t old_umask = umask(0);
+
+    int fd = open(path, O_CREAT | O_WRONLY | O_EXCL, mode);
+    if (fd < 0) {
+        perror("open");
+        umask(old_umask);
+        return 1;
+    }
+    close(fd);
+
+    if (stat(path, &st) != 0) {
+        perror("stat");
+        unlink(path);
+        umask(old_umask);
+        return 1;
+    }
+
+    mode_t got = st.st_mode & 07777;
+    unlink(path);
+    umask(old_umask);
+
+    if (got != mode) {
+        fprintf(stderr, "FAIL: open(O_CREAT, 0%04o) -> stat 0%04o\n", mode, got);
+        return 1;
+    }
+    return 0;
+}
+
+static int test_mkdir_mode(mode_t mode) {
+    const char *path = "test-db-mode-dir-tmp";
+    struct stat st;
+
+    rmdir(path);
+
+    mode_t old_umask = umask(0);
+
+    if (mkdir(path, mode) != 0) {
+        perror("mkdir");
+        umask(old_umask);
+        return 1;
+    }
+
+    if (stat(path, &st) != 0) {
+        perror("stat");
+        rmdir(path);
+        umask(old_umask);
+        return 1;
+    }
+
+    mode_t got = st.st_mode & 07777;
+    rmdir(path);
+    umask(old_umask);
+
+    if (got != mode) {
+        fprintf(stderr, "FAIL: mkdir(0%04o) -> stat 0%04o\n", mode, got);
+        return 1;
+    }
+    return 0;
+}
+
+int main(void) {
+    int failures = 0;
+    int total = 0;
+
+    /* Test all octet values simultaneously: 00000, 01111, 02222, ..., 07777 */
+    mode_t modes[] = {
+        00000, 01111, 02222, 03333, 04444, 05555, 06666, 07777,
+    };
+    int num_modes = sizeof(modes) / sizeof(modes[0]);
+
+    for (int i = 0; i < num_modes; i++) {
+        total++;
+        if (test_creat_mode(modes[i]) != 0)
+            failures++;
+    }
+
+    for (int i = 0; i < num_modes; i++) {
+        total++;
+        if (test_mkdir_mode(modes[i]) != 0)
+            failures++;
+    }
+
+    if (failures > 0) {
+        fprintf(stderr, "%d/%d mode tests failed\n", failures, total);
+        return 2;
+    }
+    return 0;
+}
diff --git a/test/test-db-mode.sh b/test/test-db-mode.sh
new file mode 100755
index 0000000..b3e97ad
--- /dev/null
+++ b/test/test-db-mode.sh
@@ -0,0 +1,10 @@ 
+#!/bin/bash
+#
+# SPDX-License-Identifier: LGPL-2.1-only
+#
+# Test that PSEUDO_DB_MODE correctly reconstructs permission bits
+# at file/directory creation time.
+
+trap "rm -rf test-db-mode-tmp test-db-mode-dir-tmp" EXIT
+
+./test/test-db-mode