public void CanGetCombinedForcesOnMultipleNodalDegreeOfFreedom()
        {
            NodalDegreeOfFreedom         nodeDof     = new NodalDegreeOfFreedom(node, DegreeOfFreedom.X);
            IList <NodalDegreeOfFreedom> nodeDofList = new List <NodalDegreeOfFreedom>(1)
            {
                nodeDof
            };

            KeyedVector <NodalDegreeOfFreedom> result = SUT.GetCombinedForcesFor(nodeDofList);

            Assert.AreEqual(1, result.Count);
            Assert.AreEqual(0, result[nodeDof]);

            SUT.ApplyForceToNode(exampleForce2, node);
            result = SUT.GetCombinedForcesFor(nodeDofList);
            Assert.AreEqual(1, result.Count);
            Assert.AreEqual(2, result[nodeDof]);
        }