Catenate
  a
 b
 

 log
 ${a}
  

 ${b}
 Catenate
  SEPARATOR=__
 GOOD
 BAY
log ${b} 

Starting test: TestProject.接口测试.TestCase02
 20170313 10:02:24.739 :  INFO : ${a} = 
 20170313 10:02:24.739 :  INFO : 
 20170313 10:02:24.755 :  INFO : ${b} = GOOD__BAY
 20170313 10:02:24.755 :  INFO : GOOD__BAY
 Ending test:   TestProject.接口测试.TestCase02