Add Extreme Conditions Test / Static Test Matrix

[JamesPHoughton]

Expanding on ideas in Lessons from software testing for developing
behavioral tests of dynamic models, create a simple way to specify extreme conditions tests for a model.

The general idea is to have a table where each row specifies a particular parameter and a value for it to take on, and then each column corresponds to the other parameters in the model. When a test condition has implications for the immediate values of one of the other parameters, these are specified in a cell. In the example from the above paper, the test matrix could look like:

	Value	Infection	Recovery
Susceptible	0	0	-
Total Population	0	0	0
Infected	0	0	0
Contact Rate	0	0	-
Recovery Time	inf	-	0
Infectivity	0	0	-

To make this type of testing easier, we should also have a function which creates a template for this type of matrix, and saves it to a file that the modeler can edit and add their constraints to. The most basic template would just take extreme conditions for each value and make them into rows.

A more advance templating function would also:

• remove rows for extreme conditions that had no downstream impact (ie, were only called in a stock's ddt function and did not influence any other variable)
• remove rows representing table functions (the table functions themselves, not the result of calls to them)
• remove columns for variables that are exogenous, and for table functions
• block off cells that are not influenced by test condition - ie, they are upstream in a feedback loop, etc.

[JamesPHoughton]

One of the problems with this method is that if you rename a variable, it won't be automatically renamed in the excel file. If you've done a lot of work filling in values for the tests, this could cause a problem.