Extract `appendView`, `destroyView` for testing

Defining `appendView` and `destroyView` in multiple tests is verbose, 
repetitious, and copy-paste-error prone.
Yes, you can have nested run's.  But it doesn't seem as though the nesting is actually needed just something like:

```javascript
destroy(container);
destroy(view);
container = view = null; // unless this is done in `destroy` helper
```