It is not necessary to specify the location of all of your tests in PicoUnit, you don't need like JUnit to add all of your classes to a TestSuite. PicoUnit will discover your tests by scanning the classpath, all you need to do is specify a starting point:

package mypackage.module;

import junit.framework.Test;

import picounit.PicoUnit;

public class Suite {
  public static Test suite() {
    PicoUnit picoUnit = new PicoUnit("Unit Tests");

    return picoUnit.generateJUnitTest();
  }
}

This 'Test Suite' is located in the package 'mypackage.module', PicoUnit will scan the classpath for all classes that implement the picounit.Test marker interface and that lie below 'mypackage.module'.