One way is you can write a policy with attribute id and try out policy using WSO2 Identity Server management console. Other way... you can start WSO2 Identity Server is debug mode and debug the your PIP attribute finder code that you have written
in UNIX, you can start as follows and debug the "getAttributeValues" method.
./wso2server.sh --debug 5005
You can find more details about writing a PIP attribute finder from here [1] which would also help you..
[1] http://xacmlinfo.org/2011/12/18/writing-jdbc-pip-module/