This also includes their Datagram counterparts: DTLSSocket and DTLSSocketWrapper.
Coverage missing for timer-related functionality, but this would require more advanced stub development.
The extra (d)tls_test_config.h is necessary for successful compilation without HW support for the mbedtls features in unittests.
I reused the mbedtls stub found in features/nanostack/coap-service/test/coap-service/unittest/stub/mbedtls_stub.c and amended it slightly with a few missing functions.