diff --git a/src/BTCSDiffusion.cpp b/src/BTCSDiffusion.cpp
index 9a92418..6c9da99 100644
--- a/src/BTCSDiffusion.cpp
+++ b/src/BTCSDiffusion.cpp
@@ -75,7 +75,7 @@ void BTCSDiffusion::simulate(std::vector<double> &c, std::vector<double> &alpha,
   A_line++;
   tripletList.push_back(T(A_line, size - 1, 1));
   // b[A_line] = bc[1];
-  if (bc[0] == -1)
+  if (bc[1] == -1)
     b[A_line] = c[c.size() - 1];
   else
     b[A_line] = this->bc[1];
diff --git a/src/BTCSDiffusion.hpp b/src/BTCSDiffusion.hpp
index cee17c9..693b8f7 100644
--- a/src/BTCSDiffusion.hpp
+++ b/src/BTCSDiffusion.hpp
@@ -2,7 +2,7 @@
 #define BTCSDIFFUSION_H_
 
 #include <vector>
-#include <Eigen/SparseCore>
+#include <Eigen/Sparse>
 
 typedef int BCSide;
 typedef Eigen::Triplet<double> T;
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 97ce3f1..9678862 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,8 +1,11 @@
 add_library(diffusion OBJECT diffusion.cpp diffusion.hpp)
 target_link_libraries(diffusion Eigen3::Eigen)
 
-add_library(diffusion_class OBJECT BTCSDiffusion.cpp)
+add_library(diffusion_class OBJECT BTCSDiffusion.cpp BTCSDiffusion.hpp)
 target_link_libraries(diffusion_class Eigen3::Eigen)
 
 add_executable(test main.cpp)
 target_link_libraries(test PUBLIC diffusion)
+
+add_executable(test_class test_class.cpp)
+target_link_libraries(test_class PUBLIC diffusion_class)
diff --git a/src/test_class.cpp b/src/test_class.cpp
index 48d8b14..fd28c85 100644
--- a/src/test_class.cpp
+++ b/src/test_class.cpp
@@ -1,5 +1,4 @@
 #include "BTCSDiffusion.hpp"
-#include "diffusion.hpp"
 #include <cmath>
 #include <iostream>
 #include <vector>
@@ -15,7 +14,7 @@ int main(int argc, char *argv[]) {
   std::vector<double> bc_left, bc_right;
 
   bc_left.push_back(5. * std::pow(10, -6));
-  bc_right.push_back(1. * std::pow(10, -6));
+  bc_right.push_back(-1);
   // input[x + 2] = 5.5556554 * std::pow(10, -6);
   // input[x + 3] = 5.234564213 * std::pow(10, -6);