You now have a Flow and in most cases you want to first test your Flow before actually deploying it. This can be done by setting up an interactive session from within the Flow Studio editor. This will temporarily deploy your Flow on a selected Node and lets you use the tools within the editor to test your Flow.
In the Flow Studio, open the debug panel by clicking on in the menu bar on the right side. This panel has two tabs, Connect and Debug. On the Connect tab open the Sandbox section and click on connect. Once connected you will see the Node name to the right above the debug panel, together with start and stop buttons.
Start the Flow by clicking on the start button in the upper right corner. The Flow will now be downloaded by the selected Node, which is a sandbox in our case, and when the Node has started executing the Flow the debug panel switches to the Debug tab.
The Debug tab is where you can see messages produced by your modules. You choose from which modules you want to see messages by toggling the debug state on each module. Hover with the mouse over a module and click on the debug button () to toggle debugging on/off. Enable debugging on the Data Generator and Aggregate modules. You should now see the messages from these two modules in the debug panel.
In our test Flow you should see five messages from the Data Generator and then one Aggregated message for these five messages. (Since our settings was to aggregate over 5 messages).