Test of derivative continuity in periodic spline

tests/TestSplineFitter.cpp

@@ -82,6 +82,12 @@ void testPeriodicSpline() {
         ASSERT_EQUAL_TOL(sin((double)i), SplineFitter::evaluateSpline(x, y, deriv, i), 0.05);
         ASSERT_EQUAL_TOL(cos((double)i), SplineFitter::evaluateSplineDerivative(x, y, deriv, i), 0.05);
     }
+    double ya[] = {15.579, 16.235, 17.325, 18.741, 20.454, 22.517, 24.944, 27.554, 29.942, 31.657,
+                   32.486, 32.612, 32.494, 32.532, 32.785, 32.917, 32.402, 30.842, 28.229, 24.989,
+                   21.762, 19.074, 17.147, 15.970, 15.467, 15.579};
+    y.assign(ya, ya+y.size());
+    ASSERT_EQUAL_TOL(SplineFitter::evaluateSplineDerivative(x, y, deriv, x[0]),
+                     SplineFitter::evaluateSplineDerivative(x, y, deriv, x[x.size()-1]), 1e-6);
 }
 
 void test2DSpline() {
@@ -177,4 +183,3 @@ int main() {
     cout << "Done" << endl;
     return 0;
 }
-