A workflow reads correctly as a diagram and behaves differently in practice more often than anyone expects. The sandbox lets you run it before customers do.
Open the workflow and start a test. The messenger opens as a customer would see it and the flow runs for real — you type, choose buttons, and follow it wherever it goes.
That's the point: reading a branch and taking it are different activities, and only one of them finds the condition that never matches.
You can run the flow as one of your actual contacts rather than as an anonymous visitor. This matters as soon as your workflow branches on who someone is.
A condition on the plan, the language, or a custom attribute can only be verified by running it as somebody who has that value — and as somebody who doesn't. Testing as yourself proves the flow works for you, which is rarely the case that breaks.
Every branch, including the ones you expect nobody to take.
That a person can still be reached at the end, whichever way the flow went.
That API steps return what you assumed, and that the flow survives when they don't.
That collected answers land on the attributes you intended — check the ticket afterwards, not just the conversation.
Testing doesn't put a workflow live — publishing does. And when something turns out wrong afterwards, unpublishing is the quickest fix: it stops the flow immediately without you having to unpick it under pressure.
