classes for filename:
 existing, writable file filename
 Unix slash style
 DOS path slash style
 filename without any extension
 filename with an extension other than “.rsf”
 5 cases in total

classes for numberOfEntities
 1 < numberOfEntities  < Integer.MAX_VALUE
  based on domain analysis we test the following values:
   1, 2, arbitrary, MAX_VALUE/2, MAX_VALUE
 4 cases in total

classes for maxDegree
 1 < maxDegree  < Integer.MAX_VALUE
  based on domain analysis we test the following values:
   1, 2, arbitrary, MAX_VALUE/2, MAX_VALUE
 4 cases in total

classes for isConnected
6.isConnected = true
7.isConnected = false
8.absolute and relative paths