diff --git a/tests/test_004_wakes_and_impedances.py b/tests/test_004_wakes_and_impedances.py
new file mode 100644
index 0000000..306b4d1
--- /dev/null
+++ b/tests/test_004_wakes_and_impedances.py
@@ -0,0 +1,65 @@
+import os, sys
+import numpy as np
+import matplotlib.pyplot as plt
+
+sys.path.append('../wakis')
+from wakis import WakeSolver as wk
+
+class TestImpedancesAndWakes:
+    def test_sin_wake(self):
+        fr = 0.5e9
+        A = 100
+        t = np.linspace(0, 100*1e-9, 3000)
+        wake = A*np.sin(2*np.pi*fr*t)
+
+        f, Z = wk.calc_impedance_from_wake([t, wake])
+        tt, wwake = wk.calc_wake_from_impedance([f, Z], samples=3000)
+        ff, Zz = wk.calc_impedance_from_wake([tt, wwake],)
+        ttt, wwwake = wk.calc_wake_from_impedance([ff,Zz], samples=3000)
+
+        assert np.allclose(wake, wwake, atol=1), '1st Transformed wake failed'
+        assert np.allclose(wake, wwwake, atol=1), '2nd Transformed wake failed'
+
+    def test_sin_impedance(self):
+        fr = 0.5e9
+        A = 100
+        t = np.linspace(0, 100*1e-9, 3000)
+        wake = A*np.sin(2*np.pi*fr*t)
+
+        f, Z = wk.calc_impedance_from_wake([t, wake])
+        tt, wwake = wk.calc_wake_from_impedance([f, Z], samples=3000)
+        ff, Zz = wk.calc_impedance_from_wake([tt, wwake],)
+
+        assert np.allclose(np.max(np.abs(Z)), A, atol=1), '1st Transformed impedance Max. failed'
+        assert np.allclose(np.max(np.abs(Zz)), A, atol=1), '2nd Transformed impedance Max. failed'
+
+        assert np.allclose(f[np.argmax(Z)], fr, atol=1e6), '1st Transformed impedance fr failed'
+        assert np.allclose(ff[np.argmax(Zz)], fr, atol=1e6), '2nd Transformed impedance fr. failed'
+
+    def plot_sin(self):
+        fr = 0.5e9
+        A = 100
+        t = np.linspace(0, 100*1e-9, 3000)
+        wake = A*np.sin(2*np.pi*fr*t)
+    
+        f, Z = wk.calc_impedance_from_wake([t, wake])
+        tt, wwake = wk.calc_wake_from_impedance([f, Z], samples=3000)
+        ff, Zz = wk.calc_impedance_from_wake([tt, wwake],)
+        ttt, wwwake = wk.calc_wake_from_impedance([ff,Zz], samples=3000)
+
+        fig, (ax1,ax2) = plt.subplots(2,1)
+        ax1.plot(t, wake, '-g', alpha=0.8, label='analytic')
+        ax1.plot(tt, wwake, '--r', alpha=0.5, label='calc')
+        ax1.plot(ttt, wwwake, '--b', alpha=0.5, label='calc, iter2')
+        ax1.set_xlabel('time [s]')
+
+        ax2.plot([fr,fr], [0., A], '-g', alpha=0.8, label='analytic')
+        ax2.plot(f, np.abs(Z), '--r', alpha=0.5, label='calc')
+        ax2.plot(ff, np.abs(Zz), '--b', alpha=0.5, label='calc, iter2')
+        ax2.set_xlabel('frequency [Hz]')
+        ax2.legend()
+
+        fig.tight_layout()
+        fig.savefig('test_004_sin.png')
+        plt.show()
+