When developing a process you can check the data going through a map shape before sending the data to your productions environment.
For a process in development or if this is something you can run in test mode... the best way to see what is going through a map shape without sending the data is to create a test copy of the process and disconnect the production (or endpoint) connector and replace it with a stop shape. This will allow you to click on the map shape to see what data went in to the map shape and then click on the stop shape (if stop shape is immediately after the map) to see what data went to the stop shape or really what the destination map sent.
Please note: The log file for the test mode process can be viewed in the top left of the canvas. The name of your process should appear as "Process: <name of process>". If you hover over this with your mouse you should be able to click on it and a drop down will appear to allow you to view the log file.
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