Move the one non-crypto-specific PSA helper macro to a new header
Create a new header file psa_helpers.h and put the one helper macro
that isn't specific to PSA crypto there. Use this header file in the
ITS test suite.
diff --git a/tests/psa_helpers.h b/tests/psa_helpers.h
new file mode 100644
index 0000000..79f6837
--- /dev/null
+++ b/tests/psa_helpers.h
@@ -0,0 +1,37 @@
+/*
+ * Helper functions for tests that use any PSA API.
+ */
+/* Copyright (C) 2019, 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 PSA_HELPERS_H
+#define PSA_HELPERS_H
+
+#if defined(MBEDTLS_PSA_CRYPTO_SPM)
+#include "spm/psa_defs.h"
+#endif
+
+/** Evaluate an expression and fail the test case if it returns an error.
+ *
+ * \param expr The expression to evaluate. This is typically a call
+ * to a \c psa_xxx function that returns a value of type
+ * #psa_status_t.
+ */
+#define PSA_ASSERT( expr ) TEST_EQUAL( ( expr ), PSA_SUCCESS )
+
+#endif /* PSA_HELPERS_H */