// setting unique messageID with the unix timestamp
String currentTimeStamp = new Date().getTime().toString();
String customerOrderRef = "TEST-RA-CA-"+currentTimeStamp;
String messageID = "TEST-"+currentTimeStamp;

// setting Test Suite property
testRunner.testCase.testSuite.setPropertyValue( "customerOrderRef", customerOrderRef );
testRunner.testCase.setPropertyValue( "messageID", messageID );