--- /dev/null
+++ libmalloc/libmalloc-474.0.13/tests/add_xzone_tests.py
@@ -0,0 +1,69 @@
+#!/usr/bin/env python3
+
+import copy
+import plistlib
+import sys
+
+def add_xzone_tests(bats_plist_path):
+    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']:
+        # Take the original test exactly as it was, unless it's xzone-only
+        if 'Tags' not in test or 'xzone_only' not in test['Tags']:
+            tests.append(test)
+
+        if 'Tags' in test and ('xzone' in test['Tags'] or 'xzone_only' in test['Tags']):
+            # 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']
+            if 'perf' not in xzone_test['Tags']:
+                # This isn't a performance test, so we can use the debug variant
+                # of the library for extra assert coverage
+                envvars.append('DYLD_LIBRARY_PATH=/AppleInternal/Tests/libmalloc/assets')
+                envvars.append('DYLD_IMAGE_SUFFIX=_testdebug')
+
+                # However, using the debug variant does prevent leaks from
+                # working, so don't bother trying
+                envvars.append('DT_BYPASS_LEAKS_CHECK=1')
+
+            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__':
+    if len(sys.argv) != 2:
+        sys.exit('Expected bats plist as argument')
+
+    add_xzone_tests(sys.argv[1])