how can we invoke custom ant task from junit

Question

I have created a ant custom task:

<taskdef name="test-connection" classname="org.common.HttpURLConnectionAntTask" >
<classpath>
<path refid="<path which has all jars required for class>" />
</classpath>
</taskdef>

i want to invoke this "test-connection" from "junit" ant task.Let me know how can it be done

System setProperty("value") is setting globally once this task definition is invoked.So want to invoke from junit so that it can be forked and the "value" will not set globally.