Hello everybody, I am new to drools. We have to integrate drools in our application. After lot of searching a found something very helpful. Here is what I did. I created a new package say test. I uploaded a new jar file which contains my model. I created a new category say banking. Then I created a rule under the banking category in test package. Finally I create a new snapshot for deployment. Then I get the changeset.xml <change-set xmlns='http://drools.org/drools-5.0/change-set' xmlns:xs='http://www.w3.org/2001/XMLSchema-instance' xs:schemaLocation='http://drools.org/drools-5.0/change-set http://anonsvn.jboss.org/repos/labs/labs/jbossrules/trunk/drools-api/src/... <add <resource source='http://localhost:8080/guvnor-5.2.0.Final-tomcat-6.0/org.drools.guvnor.Guvnor/package/Banking/Test' type='PKG' / </add</change-set Below is the code to test package com.test; import junit.framework.TestCase; import org.drools.KnowledgeBase; import org.drools.agent.KnowledgeAgent; import org.drools.agent.KnowledgeAgentConfiguration; import org.drools.agent.KnowledgeAgentFactory; import org.drools.io.ResourceFactory; import org.drools.runtime.StatefulKnowledgeSession; public class Test extends TestCase{ public void testDroolsWithGuvnor() throws Exception { KnowledgeBase knowledgeBase = createKnowledgeBase(); StatefulKnowledgeSession session = knowledgeBase.newStatefulKnowledgeSession(); try { Person person = new Person(); person.setAge(20); session.insert(person); assertTrue(session.getFactCount() == 1); session.fireAllRules(); assertTrue(session.getFactCount() == 2); } finally { session.dispose(); } } public static KnowledgeBase createKnowledgeBase(){ KnowledgeAgentConfiguration kaconf = KnowledgeAgentFactory.newKnowledgeAgentConfiguration(); kaconf.setProperty( "drools.agent.scanDirectories", "false" ); KnowledgeAgent kagent = KnowledgeAgentFactory.newKnowledgeAgent( "test agent", kaconf ); kagent.applyChangeSet( ResourceFactory.newClassPathResource("ChangeSet(12).xml")); return kagent.getKnowledgeBase(); } } But when i try to test it using junit i get the following exception. java.lang.NullPointerException at org.drools.agent.impl.KnowledgeAgentImpl.processChangeSet(KnowledgeAgentImpl.java:223) at org.drools.agent.impl.KnowledgeAgentImpl.applyChangeSet(KnowledgeAgentImpl.java:189) at org.drools.agent.impl.KnowledgeAgentImpl.applyChangeSet(KnowledgeAgentImpl.java:174) at com.test.Test.createKnowledgeBase(Test.java:34) at com.test.Test.testDroolsWithGuvnor(Test.java:15) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at junit.framework.TestCase.runTest(TestCase.java:168) at junit.framework.TestCase.runBare(TestCase.java:134) at junit.framework.TestResult$1.protect(TestResult.java:110) at junit.framework.TestResult.runProtected(TestResult.java:128) at junit.framework.TestResult.run(TestResult.java:113) at junit.framework.TestCase.run(TestCase.java:124) at junit.framework.TestSuite.runTest(TestSuite.java:243) at junit.framework.TestSuite.run(TestSuite.java:238) at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:83) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:46) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197) Dont know how to deal with this please help -- View this message in context: http://drools.46999.n3.nabble.com/java-lang-NullPointerException-while-te... Sent from the Drools: Developer (committer) mailing list mailing list archive at Nabble.com.