Back in May I responded to the question “Which advice would you give your younger (#Tester) self?” like this:

Last week I was reminded of the question as I found myself sketching the same diagram three times for three different people on three different whiteboards.

The diagram represents my mind’s-eye view of a problem space, a zone of uncertainty, a set of unresolved questions, a big cloud of don’t know with a rather fuzzy border:

What I’ll often want to do with this kind of thing is find some way to remove enough uncertainty that I can make my next move. 
For example, perhaps I am being pressed to make a decision about a project where there are many uknowns. I might try to find some aspect of the project to which I can anchor the rest and then give an answer relative to that. Something like this: “Yes, I agreed an approach in principle with Team X and until their prototype confirms the approach our detailed planning can’t start.”
I’ve still got a lot of uncertainty about exactly what I will do. But I found enough firm ground – in this case a statement in principle – that I can move the project forward.
In my head, I think of this as putting a band around the cloud and squeezing it:
And I’m left with a cleaner picture, the band effectively containing the uncertainty. Until the conditions that the band represents are confirmed or rejected I don’t have to consider the untidy insides. (Which doesn’t mean that I can’t if I want to, of course.)

A useful heuristic for me is that if I find myself thinking about the insides too much – if something I expect to be in is leaking out – then probably I didn’t tighten the band enough and I need to revisit.

When I’m exploring, the band can represent an assumption that I’m testing rather than some action that I’ve taken. “if this were true, then the remaining uncertainty would look that way and so I should be able to …”

I like this way of picturing things even though the model itself doesn’t help me with specific next moves. What it does do, which I find valuable, is remind me that when I have uncertainty I don’t have to work it out in one shot.

P.S. While writing this, I realised that I’ve effectively written it before, although in a much more technical way: On Being a Test Charter.