EVP_KDF_CTX_get_kdf_size
size_t EVP_KDF_CTX_get_kdf_size(EVP_KDF_CTX *ctx);
kdfsize = EVP_KDF_CTX_get_kdf_size(pkdfctx->kdfctx);
&& TEST_size_t_eq(EVP_KDF_CTX_get_kdf_size(kctx), SIZE_MAX)
&& TEST_size_t_eq(EVP_KDF_CTX_get_kdf_size(kctx), 0)
|| TEST_size_t_eq(EVP_KDF_CTX_get_kdf_size(kctx), SIZE_MAX))