Fix gradient descent

src/test_gradient_descent.cpp

@@ -12,7 +12,7 @@
 #include <string>
 #include <vector>
 
-TEST_CASE("Gradient Descent on functions with one dimensional argument",
+TEST_CASE("Gradient Descent on functions with multi-dimensional argument",
           "[gradient_descent]") {
     using namespace numerics;
     using std::cerr;
@@ -20,7 +20,7 @@ TEST_CASE("Gradient Descent on functions with one dimensional argument",
     using std::endl;
     FivePointDifferentiator fp;
     double step = 1e-4;
-    GradientDescent optimizer(step);
+    GradientDescent optimizer(fp, step);
 
     Coordinate<double> position1(1), position2(2), ref2(2), res1(1), res2(2);