--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/libuv/test/test-fs-fd-hash.c	Wed Jan 14 19:39:52 2026 -0800
@@ -0,0 +1,133 @@
+/* Copyright libuv project contributors. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#if defined(_WIN32) && !defined(USING_UV_SHARED)
+
+#include "uv.h"
+#include "task.h"
+
+#include "../src/win/fs-fd-hash-inl.h"
+
+
+#define HASH_MAX 1000000000
+#define HASH_INC (1000 * UV__FD_HASH_SIZE + 2)
+#define BUCKET_MAX (UV__FD_HASH_SIZE * UV__FD_HASH_GROUP_SIZE * 10)
+#define BUCKET_INC UV__FD_HASH_SIZE
+#define FD_DIFF 9
+
+
+void assert_nonexistent(int fd) {
+  struct uv__fd_info_s info = { 0 };
+  ASSERT(!uv__fd_hash_get(fd, &info));
+  ASSERT(!uv__fd_hash_remove(fd, &info));
+}
+
+void assert_existent(int fd) {
+  struct uv__fd_info_s info = { 0 };
+  ASSERT(uv__fd_hash_get(fd, &info));
+  ASSERT_EQ(info.flags, fd + FD_DIFF);
+}
+
+void assert_insertion(int fd) {
+  struct uv__fd_info_s info = { 0 };
+  assert_nonexistent(fd);
+  info.flags = fd + FD_DIFF;
+  uv__fd_hash_add(fd, &info);
+  assert_existent(fd);
+}
+
+void assert_removal(int fd) {
+  struct uv__fd_info_s info = { 0 };
+  assert_existent(fd);
+  uv__fd_hash_remove(fd, &info);
+  ASSERT_EQ(info.flags, fd + FD_DIFF);
+  assert_nonexistent(fd);
+}
+
+
+/* Run a function for a set of values up to a very high number */
+#define RUN_HASH(function)                                                   \
+  do {                                                                       \
+    for (fd = 0; fd < HASH_MAX; fd += HASH_INC) {                            \
+      function(fd);                                                          \
+    }                                                                        \
+  } while (0)
+
+/* Run a function for a set of values that will cause many collisions */
+#define RUN_COLLISIONS(function)                                             \
+  do {                                                                       \
+    for (fd = 1; fd < BUCKET_MAX; fd += BUCKET_INC) {                        \
+      function(fd);                                                          \
+    }                                                                        \
+  } while (0)
+
+
+TEST_IMPL(fs_fd_hash) {
+  int fd;
+
+  uv__fd_hash_init();
+
+  /* Empty table */
+  RUN_HASH(assert_nonexistent);
+  RUN_COLLISIONS(assert_nonexistent);
+
+  /* Fill up */
+  RUN_HASH(assert_insertion);
+  RUN_COLLISIONS(assert_insertion);
+
+  /* Full */
+  RUN_HASH(assert_existent);
+  RUN_COLLISIONS(assert_existent);
+
+  /* Update */
+  {
+    struct uv__fd_info_s info = { 0 };
+    info.flags = FD_DIFF + FD_DIFF;
+    uv__fd_hash_add(0, &info);
+  }
+  {
+    struct uv__fd_info_s info = { 0 };
+    ASSERT(uv__fd_hash_get(0, &info));
+    ASSERT_EQ(info.flags, FD_DIFF + FD_DIFF);
+  }
+  {
+    /* Leave as it was, will be again tested below */
+    struct uv__fd_info_s info = { 0 };
+    info.flags = FD_DIFF;
+    uv__fd_hash_add(0, &info);
+  }
+
+  /* Remove all */
+  RUN_HASH(assert_removal);
+  RUN_COLLISIONS(assert_removal);
+
+  /* Empty table */
+  RUN_HASH(assert_nonexistent);
+  RUN_COLLISIONS(assert_nonexistent);
+  
+  return 0;
+}
+
+#else
+
+typedef int file_has_no_tests;  /* ISO C forbids an empty translation unit. */
+
+#endif  /* ifndef _WIN32 */