diff --git a/tests/src/math.hpp b/tests/src/math.hpp
index 46bcb99..77a2b3c 100644
--- a/tests/src/math.hpp
+++ b/tests/src/math.hpp
@@ -33,18 +33,19 @@ namespace math {
     return complex(res.real()/sig.size(), res.imag()/sig.size());
   };
 
-  //TODO: implémenter la fonction
   csignal diff(const csignal& input, complex mean) {
-    return csignal();
+    csignal res;
+    for (auto x: input) {
+      res.push_back(x - mean);
+    }
+    return res;
   }
 
-  //TODO implémenter la fft
   csignal fft_rec(const csignal& input) {
     int size = input.size();
 
     if (size == 1) {
-      //TODO: que faire dans ce cas ?
-      return csignal();
+      return input;
     } else {
       csignal odd;
       csignal even;
@@ -90,7 +91,6 @@ namespace math {
     int kmax = 2*cmax;
 
     for (int m=0; m<tfd.size(); ++m) {
-      //TODO: retrouver la formule
       complex sum;
       for (int k=kmin; k<kmax; ++k) {
         sum += tfd[k]*std::exp(complex(0, 2*pi()*k*m/tfd.size()));
@@ -105,8 +105,7 @@ namespace math {
     contour res;
     csignal z = cont2sig(cont);
     complex zm = mean(z);
-    //TODO: fft(diff(z, zm));
-    csignal tfd = fft(z);
+    csignal tfd = fft(diff(z, zm));
     return coef2cont(tfd, zm, 0, cmax);
   };