diff --git a/eo/contrib/mathsym/GNUmakefile b/eo/contrib/mathsym/GNUmakefile
index 7da7683d5..47235658b 100644
--- a/eo/contrib/mathsym/GNUmakefile
+++ b/eo/contrib/mathsym/GNUmakefile
@@ -39,7 +39,7 @@ libsym.a: $(OBJS)
 	rm libsym.a; ar cq $(SYMLIB) $(OBJS) 
 
 check: $(TESTPROGRAMS)
-	test/test_compile && test/testeo && test_simplify && echo "all tests succeeded"
+	test/test_compile && test/testeo && test/test_simplify && test/test_diff && echo "all tests succeeded"
 
 test/test_compile: test/test_compile.o ${SYMLIB}
 	$(CXX) -o test/test_compile test/test_compile.o $(SYMLIB) ${LIBS}
diff --git a/eo/contrib/mathsym/test/test_diff.cpp b/eo/contrib/mathsym/test/test_diff.cpp
new file mode 100644
index 000000000..09dd292d4
--- /dev/null
+++ b/eo/contrib/mathsym/test/test_diff.cpp
@@ -0,0 +1,17 @@
+#include <Sym.h>
+#include <FunDef.h>
+#include <iostream>
+
+using namespace std;
+
+int main() {
+    
+    Sym v = SymConst(1.2);
+
+    Sym g = exp(-sqr(v));
+
+    cout << g << endl;
+    cout << differentiate(g, v.token()) << endl;
+    
+}
+
diff --git a/eo/contrib/mathsym/test/test_simplify.cpp b/eo/contrib/mathsym/test/test_simplify.cpp
new file mode 100644
index 000000000..73c94c59c
--- /dev/null
+++ b/eo/contrib/mathsym/test/test_simplify.cpp
@@ -0,0 +1,18 @@
+
+#include <FunDef.h>
+
+using namespace std;
+
+int main() {
+    
+    Sym c1 = SymConst(0.4);
+    Sym c2 = SymConst(0.3);
+    Sym v1 = SymVar(0);
+
+    Sym expr = (c1 + c2) * ( (c1 + c2) * v1);
+    
+    cout << expr << endl;
+    cout << simplify(expr) << endl;
+    
+}
+
diff --git a/eo/contrib/mathsym/test/testeo.cpp b/eo/contrib/mathsym/test/testeo.cpp
index 8693bd164..a15303cb0 100644
--- a/eo/contrib/mathsym/test/testeo.cpp
+++ b/eo/contrib/mathsym/test/testeo.cpp
@@ -102,7 +102,7 @@ int main() {
     cout << "****** Evaluation **********" << endl;
     
     Dataset dataset;
-    dataset.load_data("problem4.dat");
+    dataset.load_data("test_data.txt");
     IntervalBoundsCheck check(dataset.input_minima(), dataset.input_maxima());
     ErrorMeasure measure(dataset, 0.90, ErrorMeasure::mean_squared_scaled);