diff --git a/hw3-heat-fft/test_fft.cc b/hw3-heat-fft/test_fft.cc
index 760652d0..ff6663ae 100644
--- a/hw3-heat-fft/test_fft.cc
+++ b/hw3-heat-fft/test_fft.cc
@@ -1,39 +1,59 @@
 #include "my_types.hh"
 #include "fft.hh"
 #include <gtest/gtest.h>
 
 /*****************************************************************/
 TEST(FFT, transform) {
   UInt N = 512;
   Matrix<complex> m(N);
 
   Real k = 2 * M_PI / N;
   for (auto&& entry : index(m)) {
     int i = std::get<0>(entry);
     int j = std::get<1>(entry);
     auto& val = std::get<2>(entry);
     val = cos(k * i);
   }
 
   Matrix<complex> res = FFT::transform(m);
 
   for (auto&& entry : index(res)) {
     int i = std::get<0>(entry);
     int j = std::get<1>(entry);
     auto& val = std::get<2>(entry);
     if (std::abs(val) > 1e-10)
       std::cout << i << "," << j << " = " << val << std::endl;
 
     if (i == 1 && j == 0)
       ASSERT_NEAR(std::abs(val), N * N / 2, 1e-10);
     else if (i == N - 1 && j == 0)
       ASSERT_NEAR(std::abs(val), N * N / 2, 1e-10);
     else
       ASSERT_NEAR(std::abs(val), 0, 1e-10);
   }
 }
 /*****************************************************************/
 
 TEST(FFT, inverse_transform) {
+
+    UInt N = 512;
+    Matrix<complex> m(N);
+    Real k = 2 * M_PI / N;
+    for (auto&& entry : index(m)) {
+        int i = std::get<0>(entry);
+        int j = std::get<1>(entry);
+        auto& val = std::get<2>(entry);
+        val = cos(k * i);
+    }
+    Matrix<complex> dft_m        = FFT::transform(m);
+    Matrix<complex> invdft_dft_m = FFT::itransform(dft_m);
+
+    for (auto&& entry : index(invdft_dft_m)) {
+        int i = std::get<0>(entry);
+        int j = std::get<1>(entry);
+        auto& val = std::get<2>(entry);
+        ASSERT_NEAR(val.real(), cos(k*i), 1e-10);
+    }
+
 }
 /*****************************************************************/