--- /dev/null
+++ libmalloc/libmalloc-425.100.7/tests/malloc_size_test.c
@@ -0,0 +1,65 @@
+//
+//  malloc_size_test.c
+//  libmalloc
+//
+//  Tests for malloc_size() on both good and bad pointers.
+//
+
+#include <darwintest.h>
+#include <stdlib.h>
+#include <malloc/malloc.h>
+
+T_GLOBAL_META(T_META_RUN_CONCURRENTLY(true));
+
+static void
+test_malloc_size_valid(size_t min, size_t max, size_t incr)
+{
+	for (size_t sz = min; sz <= max; sz += incr) {
+		void *ptr = malloc(sz);
+		T_ASSERT_NOTNULL(ptr, "Allocate size %llu\n", (uint64_t)sz);
+		T_ASSERT_GE(malloc_size(ptr), malloc_good_size(sz), "Check size value");
+		free(ptr);
+	}
+}
+
+static void
+test_malloc_size_invalid(size_t min, size_t max, size_t incr)
+{
+	for (size_t sz = min; sz <= max; sz += incr) {
+		void *ptr = malloc(sz);
+		T_ASSERT_NOTNULL(ptr, "Allocate size %llu\n", (uint64_t)sz);
+		T_ASSERT_EQ(malloc_size(ptr + 1), 0UL, "Check offset by 1 size value");
+		T_ASSERT_EQ(malloc_size(ptr + sz/2), 0UL, "Check offset by half size value");
+		free(ptr);
+	}
+}
+
+T_DECL(malloc_size_valid, "Test malloc_size() on valid pointers, non-Nano",
+	   T_META_ENVVAR("MallocNanoZone=0"))
+{
+	// Test various sizes, roughly targetting each allocator range.
+	test_malloc_size_valid(2, 256, 16);
+	test_malloc_size_valid(512, 8192, 256);
+	test_malloc_size_valid(8192, 65536, 1024);
+}
+
+T_DECL(malloc_size_valid_nanov2, "Test malloc_size() on valid pointers for Nanov2",
+	   T_META_ENVVAR("MallocNanoZone=V2"))
+{
+	test_malloc_size_valid(2, 256, 16);
+}
+
+T_DECL(malloc_size_invalid, "Test malloc_size() on invalid pointers, non-Nano",
+	   T_META_ENVVAR("MallocNanoZone=0"))
+{
+	// Test various sizes, roughly targetting each allocator range.
+	test_malloc_size_invalid(2, 256, 16);
+	test_malloc_size_invalid(512, 8192, 256);
+	test_malloc_size_invalid(8192, 32768, 1024);
+}
+
+T_DECL(malloc_size_invalid_nanov2, "Test malloc_size() on valid pointers for Nanov2",
+	   T_META_ENVVAR("MallocNanoZone=V2"))
+{
+	test_malloc_size_invalid(2, 256, 16);
+}