2 Why We Need Model-Based Testing

Advanced Topics 251
This example shows the basics of maintaining a field map. There is an action
CreateEmployee that instantiates new objects. The action DeleteEmployee removes
a previously created employee from the state. The SetSalary action changes the
salary of a given employee (Override is a method on Map).
Trace 1 Trace 2
CreateEmployee(Employee(1)) CreateEmployee(Employee(1))
SetSalary(Employee(1), 200) CreateEmployee(Employee(2))
CreateEmployee(Employee(2)) DeleteEmployee(Employee(1))
SetSalary(Employee(2), 400)
DeleteEmployee(Employee(1))
SetSalary(Employee(2), 400)
Trace 1 and Trace 2 produce the same end state. In this state the values of the
state variables are
nextId = 3
allEmployees = Set(Employee(2))
salary = Map(Employee(2), 400)
This example shows that you can model instances using only the features introduced
in the previous chapters.
Now, let’s show this same example using C# instance fields. This is an example
of how to do object-oriented programming in NModel.
namespace Payroll2
{
class Employee : LabeledInstance
{
static Set allEmployees = Set.EmptySet;
int salary;
[Action]
static void CreateEmployee([Domain("new")] Employee emp)
{ allEmployees = allEmployees.Add(emp); }
[Action]
[Domain("allEmployees")]
void DeleteEmployee()
{ allEmployees = allEmployees.Remove(this); }
[Action]
[Domain("allEmployees")]
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