diff --git a/tests/include/test/constant_flow.h b/tests/include/test/constant_flow.h
new file mode 100644
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--- /dev/null
+++ b/tests/include/test/constant_flow.h
@@ -0,0 +1,51 @@
+/**
+ * \file constant_flow.h
+ *
+ * \brief   This file contains tools to ensure tested code has constant flow.
+ */
+
+/*
+ *  Copyright (C) 2020, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+
+#ifndef TEST_CONSTANT_FLOW_H
+#define TEST_CONSTANT_FLOW_H
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN)
+#include <sanitizer/msan_interface.h>
+
+/* Use macros to avoid messing up with origin tracking */
+#define TEST_CF_SECRET  __msan_allocated_memory
+// void __msan_allocated_memory(const volatile void* data, size_t size);
+#define TEST_CF_PUBLIC  __msan_unpoison
+// void __msan_unpoison(const volatile void *a, size_t size);
+
+#else /* MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN */
+
+#define TEST_CF_SECRET(ptr, size)
+#define TEST_CF_PUBLIC(ptr, size)
+
+#endif /* MBEDTLS_TEST_CONSTANT_FLOW_MEMSAN */
+
+#endif /* TEST_CONSTANT_FLOW_H */