--- /dev/null
+++ libmalloc/libmalloc-646.40.3/tests/xzone_testing.h
@@ -0,0 +1,111 @@
+#ifndef __XZONE_TESTING_H__
+#define __XZONE_TESTING_H__
+
+#include <darwintest.h>
+
+#include <../src/internal.h>
+
+#include "tmo_test_defs.h"
+
+#if CONFIG_XZONE_MALLOC
+
+#if defined(_MALLOC_TYPE_ENABLED) && _MALLOC_TYPE_ENABLED
+#define HAVE_MALLOC_TYPE 1
+#else
+#define HAVE_MALLOC_TYPE 0
+#endif
+
+extern malloc_zone_t **malloc_zones;
+extern int32_t malloc_num_zones;
+
+static inline void
+assert_zone_is_xzone_malloc(malloc_zone_t *zone)
+{
+	T_ASSERT_GE(zone->version, 14, "zone version");
+	T_ASSERT_EQ(zone->introspect->zone_type, MALLOC_ZONE_TYPE_XZONE,
+			"zone is xzone malloc");
+}
+
+static inline xzm_malloc_zone_t
+get_default_xzone_zone(void)
+{
+	malloc_zone_t *dz = malloc_zones[0];
+	assert_zone_is_xzone_malloc(dz);
+
+	return (xzm_malloc_zone_t)dz;
+}
+
+static inline xzm_malloc_zone_t
+get_default_xzone_helper_zone(void)
+{
+	T_ASSERT_GE(malloc_num_zones, 2, "malloc_num_zones sufficient");
+	malloc_zone_t *dz = malloc_zones[1];
+	assert_zone_is_xzone_malloc(dz);
+
+	return (xzm_malloc_zone_t)dz;
+}
+
+#define _TEST_STRINGIFY(x) #x
+#define TEST_STRINGIFY(x) _TEST_STRINGIFY(x)
+
+#define PTR_BUCKET_ENVVAR "MallocXzonePtrBucketCount=" \
+		TEST_STRINGIFY(XZM_XZONE_DEFAULT_POINTER_BUCKET_COUNT)
+
+static inline void
+validate_bucket_distribution(xzm_malloc_zone_t zone, const char *expr,
+		void **ptrs, size_t n, bool do_free)
+{
+	size_t counts[XZM_XZONE_DEFAULT_POINTER_BUCKET_COUNT] = { 0 };
+
+	size_t early_count = 0;
+	for (int i = 0; i < n; i++) {
+		void *p = ptrs[i];
+
+		T_QUIET; T_ASSERT_NOTNULL(p, "(%s) allocation not NULL", expr);
+
+		xzm_slice_kind_t kind;
+		xzm_segment_group_id_t sgid;
+		xzm_xzone_bucket_t bucket;
+		bool lookup = xzm_ptr_lookup_4test(zone, p, &kind, &sgid, &bucket);
+
+		if (i == 0) {
+			size_t size = malloc_size(p);
+			T_LOG("(%s) malloc_size %zu", expr, size);
+		}
+
+		if (do_free) {
+			free(p);
+		}
+
+		if (!lookup) {
+			early_count++;
+			continue;
+		}
+
+		T_QUIET; T_ASSERT_EQ((int)kind, XZM_SLICE_KIND_TINY_CHUNK,
+				"tiny chunk");
+		T_QUIET; T_ASSERT_EQ((int)sgid, XZM_SEGMENT_GROUP_POINTER_XZONES,
+				"xzone pointer segment group");
+		T_QUIET; T_ASSERT_GE(bucket, XZM_XZONE_BUCKET_POINTER_BASE,
+				"pointer bucket lower bound");
+		T_QUIET; T_ASSERT_LT(bucket,
+				XZM_XZONE_BUCKET_POINTER_BASE +
+						XZM_XZONE_DEFAULT_POINTER_BUCKET_COUNT,
+				"pointer bucket upper bound");
+
+		counts[bucket - XZM_XZONE_BUCKET_POINTER_BASE]++;
+
+	}
+
+	T_LOG("(%s) %zu early allocations", expr, early_count);
+
+	for (int i = 0; i < XZM_XZONE_DEFAULT_POINTER_BUCKET_COUNT; i++) {
+		T_EXPECT_GT(counts[i], (size_t)0,
+				"(%s) expected nonzero allocations for bucket %d, found %zu",
+				expr, i, counts[i]);
+	}
+}
+
+#endif // CONFIG_XZONE_MALLOC
+
+#endif // __XZONE_TESTING_H__