taskSession.findTaskInstances( ... ) error

[matafy]

My processdefinition.xml is below:
<?xml version="1.0" encoding="UTF-8"?>
<process-definition name="test">
<start-state name="start">

</start-state>
<task-node name="pre state">




</task-node>
........


ProcessInstance processInstance = new ProcessInstance( definition );
Token token = processInstance.getRootToken();
token.signal();
System.out.println( "now, it's at " + token.getNode().getName() );
System.out.println( "now, it's waiting for " + taskInstance.getActorId() + " to handle" );
...savePrcessInstance( processInstance );
...

TaskMgmtSession taskSession = jbpmSession.getTaskMgmtSession();
List list = taskSession.findTaskInstances( "tester" );
System.out.println( "tester now has " + list.size() + " tasks" );

when executes, it prints out as follows:
now, it's at pre state
now, it's waiting for tester to handle
...
tester now has 0 tasks.

Why tester only has 0 task?

[matafy]

sorry, the process definition is:
<process-definition name="test">
<start-state name="start">

</start-state>
<task-node name="pre state">



......

[matafy]

why it can't display collectly?
<process-definition name="toushu">
<start-state name="start">

</start-state>
<task-node name="pre state">



....