It is a merge.
From: Daniel Zapata [mailto:dzapata@...]
Sent: Thursday, December 06, 2012 1:34 PM
Subject: [Cobertura-devel] how does flushing work, merge or overwrite?
I'm running cobertura in tomcat and using the coberturaFlush servlet to persist coverage data. When you run the flush servlet, does that overwrite the existing cobertura.ser file, or does it merge the coverage data in memory with the existing cobertura file?
My use case is that I'm running cobertura in production and would like to set up some automation for periodically pulling the coverage results. Depending on the answer to the above question, I may need to collect each cobertura.ser file generated and then do a merge on them all to get an accurate report.