Hi @Planet Bake, 

Welcome to the Klaviyo Community forum. So, a couple of things I want to call out as resources here: 

With Klaviyo, you can preview an event-based flow message by choosing a recent event to preview with. You’ll be able to scroll and choose from the 10 most recent events that match the flow's trigger. There’s actually a few different ways you can test different types of flows, so I’d recommend checking out this article on testing and previewing flows for more details. Some best practices for testing flow logic: 

• If the flow you've created is based on a built-in Klaviyo idea or it's very simple and doesn't need flow filters, for example, a welcome series when someone subscribes to your newsletter, you can set all messages in the flow to live and skip testing the flow logic.
• If you set a flow to Manual and notice that nobody is entering your flow, it likely means your filters are too restrictive or the logic is keeping everyone out. Try creating a segment that mirrors your flow's setup and see if any contacts populate.

You can also check your flow logic by using the Trigger Preview Setup tool. One thing to call out here is that you cannot preview the flow logic for flows with no real qualified sample recipients. 

For your question on Abandoned Cart...perhaps this question answered by @mike.hoang might be helpful? 

He shares that there are essentially 2 abandoned cart flows:

Added to Cart Abandoned Cart - this flow requires an additional code snippet to be added to your e-comm platform. With that snippet, Klaviyo will know when someone adds an item to their cart and doesn’t purchase. 

Abandoned Cart/Checkout - this flow does not typically require an additional code snippet as the checkout started information is usually passed over through your e-commerce integration. With that said, this flow will trigger when someone actually adds something to their cart and continues the checkout process without purchasing or placing their order. 

Hopefully this info is helpful! 
Thanks, 
-Cass.