An automation has a lot of moving parts, so it's easy for something to slip. The wrong email goes out, the flow doesn't make sense, or contacts end up somewhere with nowhere to go. The fix is simple: run through the automation yourself before your contacts do. Here's how.
Start with the automation checklist. It shows any elements you haven't finished setting up, and it won't let you publish until they're done. Then make sure every path ends on purpose. Any "What happens next?" left open at the bottom of a path should get an End element.
You don't want to wait a year to test a year-long newsletter. So, for the test, shorten your waits. Click Edit, open each Some time passes wait, and change it from days to just a few minutes. Or delete the wait entirely.
Write down each original setting, because you'll put them back afterward. Your edits don't go live until you publish, and contacts sitting on an element you delete are removed from the map. So it's best to test before real contacts are on it.
Next, you need a test contact. Use yourself. If the automation starts when someone fills out a form, fill out the form yourself. If it's for contacts already in your account, select your own record in Contacts, choose Automations on the action bar, and add yourself. You'll come in through the map's Added to Automation trigger, so make sure that trigger leads where you want.
Now do whatever starts the automation, like submitting the form or visiting the page. Then open the map, click Performance in the top right, set the date range to include today, and check that you show up.
To follow just your test contact, copy your record ID from the system information tab or the record's URL. Add "&contact_id=" and the ID to the end of the Performance Mode address, and refresh. A 1 marks each element you've passed through, and a yellow circle shows where you're waiting.
Walk through each action on the path and check that it did its job. Did the right emails arrive? Your record's contact log lists the emails sent to you. Were the right tasks assigned to the right people? Did your tags change? The Automations and Tags section on your record shows your tags and automations, and the automation log shows the changes your automations made. If the map sends a webhook, check that the receiving app got it.
Next, do each thing a goal is waiting for. Submit the form, visit the page, complete the task with each outcome, or update the field. After each one, check that you moved to the right spot and that the actions under that goal ran, in the right order. If the map has several goals, you may need several test runs. And if a goal can only be activated once per contact, use a fresh test contact for each run.
Also test the path for people who don't reach the goal. By default, the wait above a goal moves contacts on only when they achieve it. To give everyone else a way forward, edit that wait, choose Some time passes in the Wait here until dropdown, and end that path with an End or a Go To.
Then go back to Performance Mode and check where you ended up. Did you land where you expected? Are you in more than one place at once? That happens when a trigger or goal is set to Add here again. Make sure that's what you want.
And check any wait set to A specific date arrives. If Ignore the year is unchecked, anyone who reaches that wait after the date is held there indefinitely.
When everything checks out, fix what you found, put your waits back to their original settings, and click Publish, then Save & Publish.
So: check the map, shorten the waits, run yourself through it, check every action and goal, then restore your waits and publish. Next up: version history, where you can look back at every published version of your automation.