private IAssociation ab, bc, cd;
@Before
public void setUp() throws Exception
{
a = new Activity("A");
b = new Activity("B");
c = new Activity("C");
d = new Activity("D");
ab = new DirectedAssociation(a, b);
bc = new DirectedAssociation(b, c);
cd = new DirectedAssociation(c, d);
model = new BPMNModel();