I am stuck trying to do TDD. I'd rather seek the counsel of others who have gone before rather than waste time with trial and error. 

**QUESTION:**

**What diagrams / exercises / development processes can I insert between "foggy notion of what system is supposed to do" (aka Conception) and "Write Test"?**

![enter image description here][1]

Anything else included in this question is simply additional information to help communicate / clarify my question; not to change the question in any way. I do not care what diagrams / exercises / development processes I use, as long as they get me unstuck.

When I say **Conception** I just mean a foggy informal mental-only notion of what a system should / can / will / might do.

**FORM OF ANSWER:**

I'm trying to navigate from conception to Unit Test in my development process. I'm looking for a way, a path, a road map, a bridge. An answer might look something like this:

> do a `xyxyx` type diagram to get the `aaaas`, then take all the
> `aaaas` and do a `wywywyw` diagram, then all the `ccccs` on the
> `wywywyw` diagram will be the classes you need to unit test and the
> `lllllls` will be the scenarios of the tests.



**PROBLEM BACKGROUND:**

I found a TDD flowchart and converted it to a Google Drawing. I'm using **NUnit**. I have studied TDD, know what it is and practiced it somewhat. This flow chart is for TDD only; no steps before Unit Testing are included.

![enter image description here][2]
The flowchart starts out with "Write Test". I had my concept, nothing I had read said I needed anything else first, so I tried following the flow chart. It was too much of a leap to go from "foggy notion" to Unit Test. This caused me "designer's block". Then I read someone say "just do it!" I tried that, but the resulting tests and ensuing code wandered somewhat aimlessly since there was nothing to guide what tests to write.

**ATTEMPTS AT SOLUTION:**

Some ideas I have explored already that seem helpful (but the question is not about these things):

 - BDD (I used **SpecFlow**)
 - **use case diagrams**

SpecFlow starts with a verbal description of a "feature" and creates tests that NUnit can run; they don't look like the unit tests I created manually but maybe I'll figure out how they relate to one another.

Use cases helped me get convert the initial foggy notion into a formal description, which was a bit of sunshine. I used **Visual Studio 2013** for that. I don't see any facility (in Visual Studio at least) to convert my use case into Unit Tests, although I found some evidence that this is one purpose of a use case. Quoting from the UML User Guide, 2nd ed., p.246:

> A use case diagram can be forward engineered to form tests for the
> element to which it applies.

*And* it looks like Visual Studio maybe wants to convert it because it can store template data on the use case and has "Code Generation Settings"

Here is a picture of what I have tried so far
![enter image description here][3]

**SUMMARY:**

![enter image description here][4]


 [1]: https://i.sstatic.net/klPY9.png
 [2]: https://i.sstatic.net/UF2Yz.png
 [3]: https://i.sstatic.net/XNNMF.png
 [4]: https://i.sstatic.net/5H9AF.png