Widgets and testing

[bear]

I'd like to express my (slightly sarcastic) appreciation for how custom widget development is achieved for those of us that aren't as skilled as others. 
To make one, in this case calling results from a different database to display in the admin widgets, I take the example and add in what I think is the right code (mysqli calls, queries, etc). So much as a tiny syntax error takes down the entire system with "Oops!". I then get to quickly remove the widget entirely and start over, needing to trawl through server error logs to get the cause.  Every time. This "not at all graceful" failure makes development daunting to say the least.

Better still is if it runs to the point of allowing the widget to appear, but without any db results in it. No hints where it fell over, if it fell over, or if it's a query issue, a display call and so on.
Troubleshooting these is nightmarish. 

Have I missed a "sandbox" method for testing widget code that would allow me to try and repeat without nuking the whole of the admin interface with each attempt?