--- /dev/null
+++ libmalloc/libmalloc-521.100.59/tests/add_xzone_tests.py
@@ -0,0 +1,94 @@
+#!/usr/bin/env python3
+
+import copy
+import plistlib
+import sys
+import argparse
+from os.path import exists
+
+def add_xzone_tests(bats_plist_path, disable_xzone):
+    with open(bats_plist_path, 'rb') as bats_plist_file:
+        orig_bats_plist = plistlib.load(bats_plist_file)
+
+    # Copy all the top-level keys as-is except for the Tests list
+    new_bats_plist = { k: v for k, v in orig_bats_plist.items() if k != 'Tests' }
+
+    tests = []
+    for test in orig_bats_plist['Tests']:
+        # Keep the original test, unless it's xzone-only
+        if 'Tags' not in test or 'xzone_only' not in test['Tags']:
+            test_copy = copy.deepcopy(test)
+            # Explicitly disable xzone malloc, so that the old allocator is
+            # still tested on platforms that have xzone malloc by default
+            envvars = ['MallocSecureAllocator=0']
+            if 'ShellEnv' in test_copy:
+                test_copy['ShellEnv'].extend(envvars)
+            else:
+                test_copy['ShellEnv'] = envvars
+            tests.append(test_copy)
+
+        if 'Tags' in test and ('xzone' in test['Tags'] or 'xzone_only' in test['Tags']) and \
+                not disable_xzone:
+            # This test has been tagged to run with xzone malloc
+            xzone_test = copy.deepcopy(test)
+
+            if 'TestName' in xzone_test:
+                orig_name = xzone_test['TestName']
+                xzone_test['TestName'] = orig_name + '.xzone'
+
+            if 'CanonicalName' in xzone_test:
+                # The CanonicalName for darwintests has a .<arch> suffix that we
+                # want to keep at the end, so insert our new component just
+                # before that
+                orig_name = xzone_test['CanonicalName']
+                components = orig_name.split('.')
+                if len(components) > 1:
+                    components.insert(-1, 'xzone')
+                    new_name = '.'.join(components)
+                else:
+                    new_name = orig_name + '.xzone'
+
+                xzone_test['CanonicalName'] = new_name
+
+            envvars = [
+                'MallocSecureAllocator=1',
+                'MallocSecureAllocatorNano=1',
+            ]
+            if 'perf' not in xzone_test['Tags'] and \
+                    'no_debug' not in xzone_test['Tags'] and \
+                    not xzone_test.get('TestName', '').startswith('libmalloc.pgm'):
+                # This isn't a performance test or otherwise incompatible with
+                # the debug variant of the library, so we can use it for extra
+                # assert coverage.
+                #
+                # PGM tests can't use the debug variant until rdar://114584236
+                # is addressed
+                envvars.append('DYLD_IMAGE_SUFFIX=_debug')
+
+            if 'ShellEnv' in xzone_test:
+                xzone_test['ShellEnv'].extend(envvars)
+            else:
+                xzone_test['ShellEnv'] = envvars
+
+            tests.append(xzone_test)
+
+    new_bats_plist['Tests'] = tests
+
+    with open(bats_plist_path, 'wb') as bats_plist_file:
+        plistlib.dump(new_bats_plist, bats_plist_file, fmt=plistlib.FMT_BINARY)
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(description='Adds xzone malloc tests to BATS plist')
+    parser.add_argument('bats_plist')
+    parser.add_argument('-p', '--platform', help='Platform tests are being run on ()')
+    args = parser.parse_args()
+
+    assert exists(args.bats_plist), 'Expected bats plist as argument'
+
+    disable_xzone_tests = False
+    if args.platform == 'WatchOS':
+        # MallocSecureAllocator=1 is a no-op on arm64_32 (read: all watches),
+        # so don't generate .xzone test variants on watchOS
+        disable_xzone_tests = True
+
+    add_xzone_tests(args.bats_plist, disable_xzone_tests)