This requires support from the framework unfortunately. The issue is that the BaseRunner class will always automatically purge the output directory, and there is no hook into the framework to allow you to avoid this. You can for instance move the output subdirectory manually you want to re-run the validation over to say 'repeat' (same directory level), and then use;
from pysys.constants import *
from pysys.basetest import BaseTest
class PySysTest(BaseTest):
def execute(self):
if self.mode=='repeat': pass
def validate(self):
if self.mode=='repeat':
self.output=os.path.join(self.descriptor.output, 'repeat')
where I have ommitted the implementations of the execute and validate. You would need to add the mode into the descriptor for the test
<classification>
<groups>
<group></group>
</groups>
<modes>
<mode>repeat</mode>
</modes>
</classification>
and run using "pysys.py run -mrepeat". This would help with the debugging if your execute takes a long time, but probably not want you want out-of-the-box i.e. a top level option to the runner to just perform validation over a previously run test. I'll add a feature request for this.