diff --git a/src/test/java/org/apache/commons/math4/ode/TestProblem1.java b/src/test/java/org/apache/commons/math4/ode/TestProblem1.java
index 27409203b..62ad22252 100644
--- a/src/test/java/org/apache/commons/math4/ode/TestProblem1.java
+++ b/src/test/java/org/apache/commons/math4/ode/TestProblem1.java
@@ -56,16 +56,16 @@ public class TestProblem1
   public void doComputeDerivatives(double t, double[] y, double[] yDot) {
 
     // compute the derivatives
-    for (int i = 0; i < n; ++i)
+    for (int i = 0; i < getDimension(); ++i)
       yDot[i] = -y[i];
 
   }
 
   @Override
   public double[] computeTheoreticalState(double t) {
-    double c = FastMath.exp (t0 - t);
-    for (int i = 0; i < n; ++i) {
-      y[i] = c * y0[i];
+    double c = FastMath.exp (getInitialTime() - t);
+    for (int i = 0; i < getDimension(); ++i) {
+      y[i] = c * getInitialState()[i];
     }
     return y;
   }
diff --git a/src/test/java/org/apache/commons/math4/ode/TestProblem2.java b/src/test/java/org/apache/commons/math4/ode/TestProblem2.java
index 27bd2c1d1..4936a02c7 100644
--- a/src/test/java/org/apache/commons/math4/ode/TestProblem2.java
+++ b/src/test/java/org/apache/commons/math4/ode/TestProblem2.java
@@ -57,7 +57,7 @@ public class TestProblem2
   public void doComputeDerivatives(double t, double[] y, double[] yDot) {
 
     // compute the derivatives
-    for (int i = 0; i < n; ++i)
+    for (int i = 0; i < getDimension(); ++i)
       yDot[i] = t * (t * t - y[i]);
 
   }
@@ -66,7 +66,7 @@ public class TestProblem2
   public double[] computeTheoreticalState(double t) {
     double t2 = t * t;
     double c = t2 + 2 * (FastMath.exp (-0.5 * t2) - 1);
-    for (int i = 0; i < n; ++i) {
+    for (int i = 0; i < getDimension(); ++i) {
       y[i] = c;
     }
     return y;
diff --git a/src/test/java/org/apache/commons/math4/ode/TestProblem5.java b/src/test/java/org/apache/commons/math4/ode/TestProblem5.java
index b3a19d558..a9ae3bafd 100644
--- a/src/test/java/org/apache/commons/math4/ode/TestProblem5.java
+++ b/src/test/java/org/apache/commons/math4/ode/TestProblem5.java
@@ -28,7 +28,7 @@ public class TestProblem5 extends TestProblem1 {
    * Simple constructor.
    */
     public TestProblem5() {
-        setFinalConditions(2 * t0 - t1);
+        setFinalConditions(2 * getInitialTime() - getFinalTime());
     }
 
 }
diff --git a/src/test/java/org/apache/commons/math4/ode/TestProblem6.java b/src/test/java/org/apache/commons/math4/ode/TestProblem6.java
index 17b65061a..b06cf77ca 100644
--- a/src/test/java/org/apache/commons/math4/ode/TestProblem6.java
+++ b/src/test/java/org/apache/commons/math4/ode/TestProblem6.java
@@ -58,7 +58,7 @@ public class TestProblem6
         double t2 = t  * t;
         double t4 = t2 * t2;
         double t5 = t4 * t;
-        for (int i = 0; i < n; ++i) {
+        for (int i = 0; i < getDimension(); ++i) {
             yDot[i] = 3 * t5 - y[i];
         }
 
@@ -66,7 +66,7 @@ public class TestProblem6
 
     @Override
     public double[] computeTheoreticalState(double t) {
-        for (int i = 0; i < n; ++i) {
+        for (int i = 0; i < getDimension(); ++i) {
             y[i] = ((((3 * t - 15) * t + 60) * t - 180) * t + 360) * t - 360;
         }
         return y;
diff --git a/src/test/java/org/apache/commons/math4/ode/TestProblemAbstract.java b/src/test/java/org/apache/commons/math4/ode/TestProblemAbstract.java
index aa4e3e0ae..e59df4579 100644
--- a/src/test/java/org/apache/commons/math4/ode/TestProblemAbstract.java
+++ b/src/test/java/org/apache/commons/math4/ode/TestProblemAbstract.java
@@ -28,22 +28,22 @@ public abstract class TestProblemAbstract
   implements FirstOrderDifferentialEquations {
 
   /** Dimension of the problem. */
-  protected int n;
+  private int n;
 
   /** Number of functions calls. */
-  protected int calls;
+  private int calls;
 
   /** Initial time */
-  protected double t0;
+  private double t0;
 
   /** Initial state */
-  protected double[] y0;
+  private double[] y0;
 
   /** Final time */
-  protected double t1;
+  private double t1;
 
   /** Error scale */
-  protected double[] errorScale;
+  private double[] errorScale;
 
   /**
    * Simple constructor.