What are Integration Tests ?
Basically there are unit tests and integration tests we need to write after writing a function or a feature. Unit tests are functional tests which are written to test that the written piece of code is working in expected way.Integration tests are written to automate working scenarios. for example
in WSO2 ESB if we need to send a message to BE through ESB we need to manually configure ESB for such scenario. (deploying configuration,Sending message through client..etc). So all steps done in manually are need to be automate in Integration Tests.
Architecture used when writing Integration Tests
Technically as standard and practise we are using following architecture when writing integration tests. 
We have admin services written in ESB .So UI calls admin services via service stubs.So when wrtting tests we need to do it in same manner. We have admin clients written using service stubs and those admin clients used in Integration Util classes for write Tests.
Writing Integration Tests
When you writing Integration test for WSO2 ESB. you need to checkout product-esb from wso2 git repository[1]. Then you don't need to build whole product-esb.if you can it is ok.if there are built failures then you can copy already built zip file of ESB and put it under
product-esb/modules/distribution/target
and then build from inside the integration module. Integration module consists of admin clients and Integration test utils and actual integration tests.
We are using testng as testing framework and so we have dependency for testng. we need to add entries for the tests we written to the testng.xml file. which resides in the resources folder of test module.
Debugging Integration Tests
you can use following commands for debug Integration tests
-Dmaven.surefire.debug
Or you can add following configuration to the surefire plugin configuration in pom.xml file.
-Xms512m -Xmx1024m -XX:MaxPermSize=128m -Xmx1024m -XX:PermSize=256m -XX:MaxPermSize=512m -Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=5006
