public void LinearBasicStepTest()
            {
                World w = new World ();
                Rigid r = new Rigid (10, new Matrix (1, 1, 1));
                w.AddRigid (r);
                w.AddEffect (new Force (new Vector (1, 0, 0), r));
                State s = new State (w, 0.001);
                s.InitState ();
                s.ForwardStep ();

                Assert.AreEqual (10, s.RigidStates [r].Mass, 0.0001);
                Assert.AreEqual (1, s.RigidStates [r].StateForceList.Force.X, 0.001);
                Assert.AreEqual (0.1, s.RigidStates [r].LinearAcceleration.X, 0.001);
            }
            public void OneWorldTwoStatesTest()
            {
                World w = new World ();

                Rigid r1 = new Rigid (30, new Matrix (70, 70, 70));
                w.AddRigid (r1);
                w.AddEffect (new Force (new Vector (30, 0, 0), r1, new Vector (5, 0, 0)));
                w.AddEffect (new Moment (new Vector (0, 0, 50), r1));

                Rigid r2 = new Rigid (5, new Matrix (200, 200, 200));
                r2.StartCenterOfMass = new Vector (10, 10, 10);
                w.AddRigid (r2);
                w.AddEffect (new Force (new Vector (10, 0, 0), r2, new Vector (0, -100, 0)));

                State s1 = new State (w, 0.0001);
                State s2 = new State (w, 0.001);

                s1.Simulate (1);
                s2.Simulate (2);
                s1.ForwardStep ();

                Assert.AreEqual (0, s1.RigidStates [r1].LinearAcceleration.Y, 0.1);
                Assert.AreEqual (0, s1.RigidStates [r1].LinearVelocity.Y, 0.1);
                Assert.AreEqual (0, s1.RigidStates [r1].CenterOfMass.Y, 0.1);
                Assert.AreEqual (1, s1.RigidStates [r1].LinearAcceleration.X, 0.1);
                Assert.AreEqual (1, s1.RigidStates [r1].LinearVelocity.X, 0.1);
                Assert.AreEqual (0.5, s1.RigidStates [r1].CenterOfMass.X, 0.1);

                Assert.AreEqual (0.71, s1.RigidStates [r1].AngularAcceleration.Z, 0.1);
                Assert.AreEqual (0.71, s1.RigidStates [r1].AngularVelocity.Z, 0.1);
                Assert.AreEqual (0.36, s1.RigidStates [r1].AnglesOfRotation.Z, 0.1);

                Assert.AreEqual (0, s1.RigidStates [r2].LinearAcceleration.Y, 0.1);
                Assert.AreEqual (0, s1.RigidStates [r2].LinearVelocity.Y, 0.1);
                Assert.AreEqual (10, s1.RigidStates [r2].CenterOfMass.Y, 0.1);
                Assert.AreEqual (2, s1.RigidStates [r2].LinearAcceleration.X, 0.1);
                Assert.AreEqual (2, s1.RigidStates [r2].LinearVelocity.X, 0.1);
                Assert.AreEqual (11, s1.RigidStates [r2].CenterOfMass.X, 0.1);
                Assert.AreEqual (10, s1.RigidStates [r2].CenterOfMass.Z, 0.1);

                Assert.AreEqual (5, s1.RigidStates [r2].AngularAcceleration.Z, 0.1);
                Assert.AreEqual (5, s1.RigidStates [r2].AngularVelocity.Z, 0.1);
                Assert.AreEqual (2.5, s1.RigidStates [r2].AnglesOfRotation.Z, 0.1);

                Assert.AreEqual (0, s2.RigidStates [r1].LinearAcceleration.Y, 0.1);
                Assert.AreEqual (0, s2.RigidStates [r1].LinearVelocity.Y, 0.1);
                Assert.AreEqual (0, s2.RigidStates [r1].CenterOfMass.Y, 0.1);
                Assert.AreEqual (1, s2.RigidStates [r1].LinearAcceleration.X, 0.1);
                Assert.AreEqual (2, s2.RigidStates [r1].LinearVelocity.X, 0.1);
                Assert.AreEqual (2, s2.RigidStates [r1].CenterOfMass.X, 0.1);

                Assert.AreEqual (0.71, s2.RigidStates [r1].AngularAcceleration.Z, 0.1);
                Assert.AreEqual (1.43, s2.RigidStates [r1].AngularVelocity.Z, 0.1);
                Assert.AreEqual (1.43, s2.RigidStates [r1].AnglesOfRotation.Z, 0.1);

                Assert.AreEqual (0, s2.RigidStates [r2].LinearAcceleration.Y, 0.1);
                Assert.AreEqual (0, s2.RigidStates [r2].LinearVelocity.Y, 0.1);
                Assert.AreEqual (10, s2.RigidStates [r2].CenterOfMass.Y, 0.1);
                Assert.AreEqual (2, s2.RigidStates [r2].LinearAcceleration.X, 0.1);
                Assert.AreEqual (4, s2.RigidStates [r2].LinearVelocity.X, 0.1);
                Assert.AreEqual (14, s2.RigidStates [r2].CenterOfMass.X, 0.1);
                Assert.AreEqual (10, s2.RigidStates [r2].CenterOfMass.Z, 0.1);

                Assert.AreEqual (5, s2.RigidStates [r2].AngularAcceleration.Z, 0.1);
                Assert.AreEqual (10, s2.RigidStates [r2].AngularVelocity.Z, 0.1);
                Assert.AreEqual (10, s2.RigidStates [r2].AnglesOfRotation.Z, 0.1);
            }