If there is a need to provide extra xa-datasource-properties, it will not be configurable automatically, e.g.:

TEST_XA_CONNECTION_PROPERTY_Ssl=true
TEST_XA_CONNECTION_PROPERTY_SslMode=allow 

Workaround:

Set the same property for EJB Timer datasource:

EJB_TIMER_XA_CONNECTION_PROPERTY_Ssl=true
EJB_TIMER_CONNECTION_PROPERTY_SslMode=allow