diff --git a/library/psa_crypto_driver_wrappers.c b/library/psa_crypto_driver_wrappers.c
index d41209bbf..a8dcc064d 100644
--- a/library/psa_crypto_driver_wrappers.c
+++ b/library/psa_crypto_driver_wrappers.c
@@ -256,23 +256,51 @@ static psa_status_t get_expected_key_size( const psa_key_attributes_t *attribute
                                            size_t *expected_size )
 {
     size_t buffer_size = 0;
-    if( PSA_KEY_LIFETIME_GET_LOCATION( attributes->core.lifetime ) == PSA_KEY_LOCATION_LOCAL_STORAGE )
-    {
-        buffer_size = PSA_KEY_EXPORT_MAX_SIZE( attributes->core.type,
-                                               attributes->core.bits );
+    psa_key_location_t location = PSA_KEY_LIFETIME_GET_LOCATION( attributes->core.lifetime );
+    psa_key_type_t key_type = attributes->core.type;
+    size_t key_bits = attributes->core.bits;
 
-        if( buffer_size == 0 )
+    switch( location )
+    {
+        case PSA_KEY_LOCATION_LOCAL_STORAGE:
+            buffer_size = PSA_KEY_EXPORT_MAX_SIZE( key_type, key_bits );
+
+            if( buffer_size == 0 )
+                return( PSA_ERROR_NOT_SUPPORTED );
+
+            *expected_size = buffer_size;
+            return( PSA_SUCCESS );
+
+#if defined(PSA_CRYPTO_DRIVER_TEST)
+        case PSA_CRYPTO_TEST_DRIVER_LIFETIME:
+            /* TBD: opaque driver support: need to calculate size through a
+             * driver-defined size function, since the size of an opaque (wrapped)
+             * key will be different for each implementation. */
+#ifdef TEST_KEY_CONTEXT_SIZE_FUNCTION
+            *expected_size = test_size_function( key_type, key_bits );
+            return( PSA_SUCCESS );
+#else /* TEST_DRIVER_KEY_CONTEXT_SIZE_FUNCTION */
+            if( PSA_KEY_TYPE_IS_KEY_PAIR( key_type ) )
+            {
+                *expected_size = TEST_DRIVER_KEY_CONTEXT_BASE_SIZE
+                                 + TEST_DRIVER_KEY_CONTEXT_PUBLIC_KEY_SIZE;
+            }
+            else if( PSA_KEY_TYPE_IS_PUBLIC_KEY( attributes->core.type ) )
+            {
+                *expected_size = TEST_DRIVER_KEY_CONTEXT_BASE_SIZE
+                                 + TEST_DRIVER_KEY_CONTEXT_SYMMETRIC_FACTOR
+                                 * ( ( key_bits + 7 ) / 8 );
+            }
+            else
+            {
+                return( PSA_ERROR_NOT_SUPPORTED );
+            }
+            return( PSA_SUCCESS );
+#endif /* TEST_DRIVER_KEY_CONTEXT_SIZE_FUNCTION */
+#endif /* PSA_CRYPTO_DRIVER_TEST */
+
+        default:
             return( PSA_ERROR_NOT_SUPPORTED );
-
-        *expected_size = buffer_size;
-        return( PSA_SUCCESS );
-    }
-    else
-    {
-        /* TBD: opaque driver support: need to calculate size through a
-         * driver-defined size function, since the size of an opaque (wrapped)
-         * key will be different for each implementation. */
-        return( PSA_ERROR_NOT_SUPPORTED );
     }
 }
 #endif /* PSA_CRYPTO_DRIVER_PRESENT */
diff --git a/tests/include/test/drivers/size.h b/tests/include/test/drivers/size.h
new file mode 100644
index 000000000..4e5b5918e
--- /dev/null
+++ b/tests/include/test/drivers/size.h
@@ -0,0 +1,87 @@
+/*
+ * Test driver for context size functions
+ */
+/*  Copyright The Mbed TLS Contributors
+ *  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.
+ */
+
+#ifndef PSA_CRYPTO_TEST_DRIVERS_SIZE_H
+#define PSA_CRYPTO_TEST_DRIVERS_SIZE_H
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(PSA_CRYPTO_DRIVER_TEST)
+#include <psa/crypto_driver_common.h>
+
+typedef struct {
+    unsigned int context;
+} test_driver_key_context_t;
+
+/** \def TEST_DRIVER_KEY_CONTEXT_BASE_SIZE
+ *
+ * This macro returns the base size for the key context. It should include
+ * the size for any driver context information stored with each key.
+ */
+#define TEST_DRIVER_KEY_CONTEXT_BASE_SIZE          sizeof(test_driver_key_context_t)
+
+/** \def TEST_DRIVER_KEY_CONTEXT_KEY_PAIR_SIZE
+ *
+ * Number of bytes included in every key context for a key pair.
+ */
+
+#define TEST_DRIVER_KEY_CONTEXT_KEY_PAIR_SIZE      0
+
+/** \def TEST_DRIVER_KEY_CONTEXT_PUBLIC_KEY_SIZE
+ *
+ * Number of bytes included in every key context for a public key.
+ */
+#define TEST_DRIVER_KEY_CONTEXT_PUBLIC_KEY_SIZE    0
+
+/** \def TEST_DRIVER_KEY_CONTEXT_SYMMETRIC_FACTOR
+ *
+ * Every key context for a symmetric key includes this many times the key size.
+ */
+#define TEST_DRIVER_KEY_CONTEXT_SYMMETRIC_FACTOR   0
+
+/** \def TEST_DRIVER_KEY_CONTEXT_STORE_PUBLIC_KEY
+ *
+ * If this is true for a key pair, the key context includes space for the public key.
+ * If this is false, no additional space is added for the public key.
+ */
+#define TEST_DRIVER_KEY_CONTEXT_STORE_PUBLIC_KEY   0
+
+/** \def TEST_DRIVER_KEY_CONTEXT_SIZE_FUNCTION
+ *
+ * If TEST_DRIVER_KEY_CONTEXT_SIZE_FUNCTION is defined, the test driver
+ * provides a size_function entry point, otherwise, it does not.
+ *
+ * Some opaque drivers have the need to support a custom size for the storage
+ * of key and context information. The size_function provides the ability to
+ * provide that customization.
+ */
+//#define TEST_DRIVER_KEY_CONTEXT_SIZE_FUNCTION
+
+#ifdef TEST_DRIVER_KEY_CONTEXT_SIZE_FUNCTION
+size_t test_size_function(
+    const psa_key_type_t key_type,
+    const size_t key_bits );
+#endif /* TEST_DRIVER_KEY_CONTEXT_SIZE_FUNCTION */
+
+#endif /* PSA_CRYPTO_DRIVER_TEST */
+#endif /* PSA_CRYPTO_TEST_DRIVERS_KEYGEN_H */
diff --git a/tests/include/test/drivers/test_driver.h b/tests/include/test/drivers/test_driver.h
index 7ee8e5eea..ee5974217 100644
--- a/tests/include/test/drivers/test_driver.h
+++ b/tests/include/test/drivers/test_driver.h
@@ -25,5 +25,6 @@
 #include "test/drivers/signature.h"
 #include "test/drivers/keygen.h"
 #include "test/drivers/cipher.h"
+#include "test/drivers/size.h"
 
 #endif /* PSA_CRYPTO_TEST_DRIVER_H */
diff --git a/tests/src/drivers/size.c b/tests/src/drivers/size.c
new file mode 100644
index 000000000..05f8a986a
--- /dev/null
+++ b/tests/src/drivers/size.c
@@ -0,0 +1,47 @@
+/*
+ * Test driver for retrieving key context size.
+ * Only used by opaque drivers.
+ */
+/*  Copyright The Mbed TLS Contributors
+ *  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.
+ */
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_PSA_CRYPTO_DRIVERS) && defined(PSA_CRYPTO_DRIVER_TEST)
+#include "psa/crypto.h"
+#include "psa_crypto_core.h"
+#include "mbedtls/error.h"
+
+#include "test/drivers/size.h"
+
+#include <string.h>
+
+#ifdef TEST_KEY_CONTEXT_SIZE_FUNCTION
+size_t test_size_function(
+    const psa_key_type_t key_type,
+    const size_t key_bits )
+{
+    (void) key_type;
+    (void) key_bits;
+    return 0;
+}
+#endif /*TEST_KEY_CONTEXT_SIZE_FUNCTION */
+
+#endif /* MBEDTLS_PSA_CRYPTO_DRIVERS && PSA_CRYPTO_DRIVER_TEST */