diff --git a/tests/test_spectra.py b/tests/test_spectra.py
index ac838e1..901f739 100644
--- a/tests/test_spectra.py
+++ b/tests/test_spectra.py
@@ -3,6 +3,7 @@ import pytest
 
 from scgenerator.math import abs2, wspace
 from scgenerator.physics.units import m_rads
+from scgenerator.physics.pulse import find_lobe_limits
 from scgenerator.spectra import Spectrum
 
 
@@ -90,10 +91,10 @@ def test_energy():
 def test_mask():
     wl = 800e-9
     bw = 50e-9
-    t = np.linspace(-1e-12, 1e-12, 4096)
+    n = 8192
+    t = np.linspace(-1e-12, 1e-12, n)
     w = wspace(t) + m_rads(wl)
-    spec = Spectrum(np.ones(4096) + 0j, w, t)
+    spec = Spectrum(np.ones(n) + 0j, w, t)
     mased = spec.mask_wl(wl, bw)
-    above = mased.wl_int / mased.wl_int.max() - 0.5 >= 0
-    diff = spec.wl_disp[above].max() - spec.wl_disp[above].min()
-    assert diff == bw
+    l, r = find_lobe_limits(mased.wl_disp, mased.wl_int)[1]
+    assert r - l == pytest.approx(bw, rel=1e-2, abs=1e-10)