diff --git a/src/SIM/Test/TestNewmark.C b/src/SIM/Test/TestNewmark.C
index 3829bd82..c8f69557 100644
--- a/src/SIM/Test/TestNewmark.C
+++ b/src/SIM/Test/TestNewmark.C
@@ -109,7 +109,7 @@ public:
     if (myProblem->getMode() == SIM::MASS_ONLY) {
       ElmMats elm;
       elm.resize(1,1); elm.redim(1);
-      elm.A[0].fill(M); // Mass Matrix
+      elm.A[0].fill(M); // Mass matrix
       ok = myEqSys->assemble(&elm,1);
     }
     else {
@@ -159,7 +159,7 @@ public:
       NewmarkMats elm(intPrm[0],intPrm[1],intPrm[2],intPrm[3]);
       elm.resize(3,1); elm.redim(2); elm.vec.resize(3);
       elm.setStepSize(time.dt,0);
-      elm.A[1](1,1) = elm.A[1](2,2) = M; // Mass Matrix
+      elm.A[1](1,1) = elm.A[1](2,2) = M; // Mass matrix
       elm.A[2](1,1) = elm.A[2](2,2) = K; // Stiffness matrix
       elm.A[2](2,1) = elm.A[2](1,2) = -K;
       elm.b[0] = elm.A[2]*prevSol.front(); // Elastic forces
diff --git a/src/SIM/Test/TestNonLinSIM.C b/src/SIM/Test/TestNonLinSIM.C
new file mode 100644
index 00000000..f4b628a2
--- /dev/null
+++ b/src/SIM/Test/TestNonLinSIM.C
@@ -0,0 +1,139 @@
+// $Id$
+//==============================================================================
+//!
+//! \file TestNonLinSIM.C
+//!
+//! \date Nov 25 2016
+//!
+//! \author Knut Morten Okstad / SINTEF
+//!
+//! \brief Tests the nonlinear quasi-static solution driver.
+//!
+//==============================================================================
+
+#include "SAM.h"
+#include "IntegrandBase.h"
+#include "SIMoutput.h"
+#include "SIMdummy.h"
+
+#include "NonLinSIM.h"
+#include "ElmMats.h"
+#include "AlgEqSystem.h"
+#include "TimeStep.h"
+
+#include "gtest/gtest.h"
+#include <numeric>
+
+
+// SAM class representing a single-DOF system.
+class SAM1DOF : public SAM
+{
+public:
+  SAM1DOF()
+  {
+    nmmnpc = nel = nnod = ndof = neq = 1;
+    mmnpc  = new int[1]; mmnpc[0] = 1;
+    mpmnpc = new int[2]; std::iota(mpmnpc,mpmnpc+2,1);
+    madof  = new int[2]; std::iota(madof,madof+2,1);
+    msc    = new int[1]; msc[0] = 1;
+    EXPECT_TRUE(this->initSystemEquations());
+  }
+  virtual ~SAM1DOF() {}
+};
+
+
+// Dummy integrand class.
+class Dummy : public IntegrandBase
+{
+public:
+  Dummy() : IntegrandBase(1) {}
+  virtual ~Dummy() {}
+};
+
+
+// Simulator class for a single-DOF skew bar.
+class Bar1DOF : public SIMdummy<SIMoutput>
+{
+public:
+  Bar1DOF(IntegrandBase* p) : SIMdummy<SIMoutput>(p) { mySam = new SAM1DOF(); }
+  virtual ~Bar1DOF() {}
+  virtual bool assembleSystem(const TimeDomain&, const Vectors& prevSol,
+                              bool newLHSmatrix, bool)
+  {
+    const double x = 5.0;             // Initial X-coordinate of end point
+    const double y = 2.0;             // Initial Y-coordinate of end point
+    const double K = 26925.824035673; // Axial stiffness
+    const double F = -200.0;          // External load (constant)
+
+    double u   = prevSol.front().front(); // Current deflection
+    double L   = hypot(x,y+u); // Current length of the bar
+    double L0  = hypot(x,y);   // Initial length of the bar
+    double eps = L/L0 - 1.0;   // Axial strain
+    double N   = K*eps;        // Axial force
+    double Km  = K/L0;         // Nominal material stiffness
+    double Kg  = N/L;          // Nominal geometric stiffness
+
+    Vec3 X(x/L,(y+u)/L,0.0); // Beam axis
+    Vec3 Y(-X.y,X.x,0.0);    // Normal axis
+
+    ElmMats elm;
+    elm.resize(1,1);
+    elm.redim(1);
+    elm.vec.resize(1);
+    elm.A.front().fill(Km*X.y*X.y + Kg*Y.y*Y.y); // Stiffness matrix
+    elm.b.front().fill(-N*X.y);                  // Internal forces
+    elm.vec.front() = prevSol.front();
+    myEqSys->initialize(newLHSmatrix);
+    if (!myEqSys->assemble(&elm,1))
+      return false;
+
+    // Add in the external load
+    if (!mySam->assembleSystem(*myEqSys->getVector(),&F,1))
+      return false;
+
+    return myEqSys->finalize(newLHSmatrix);
+  }
+};
+
+
+// Nonlinear simulation driver with line search.
+class TestNonLinSIM : public NonLinSIM
+{
+public:
+  TestNonLinSIM(SIMbase& sim, double lsTol = 0.0) : NonLinSIM(sim)
+  {
+    eta = lsTol;
+    rTol = 1.0e-16;
+  }
+  virtual ~TestNonLinSIM() {}
+};
+
+
+static void runSingleDof (NonLinSIM& solver, int& n, double& s)
+{
+  TimeStep tp;
+  ASSERT_TRUE(solver.initSol());
+  ASSERT_TRUE(solver.advanceStep(tp));
+  ASSERT_EQ(solver.solveStep(tp),SIM::CONVERGED);
+  s = solver.getSolution().front(); n = tp.iter;
+  std::cout <<"  Solution "<< s <<" obtained in "<< n <<" iterations.\n";
+}
+
+
+TEST(TestNonLinSIM, SingleDOF)
+{
+  Bar1DOF simulator(new Dummy());
+  ASSERT_TRUE(simulator.initSystem(0));
+
+  TestNonLinSIM integrator1(simulator);
+  TestNonLinSIM integrator2(simulator,0.0001);
+
+  int    n1, n2;
+  double s1, s2;
+  runSingleDof(integrator1,n1,s1);
+  runSingleDof(integrator2,n2,s2);
+
+  EXPECT_FLOAT_EQ(s1,s2);
+  EXPECT_EQ(n1,5);
+  EXPECT_EQ(n2,3);
+}