add unit/integrted tests for dpc

How do I know what strings to use?  Please add text describing where to find them and add the list as a function attribute.  If the list is short enough, it should be documented as an enumeration 

```
solver : {'foo', 'bar'}
     Method to solve the nonlinear fitting problem.

```

`dpc_runner.solvel = ['list', 'of', 'valid', 'strings']`