diff --git a/tests/test_sigproc.py b/tests/test_sigproc.py
index bc3cd87..70d72d7 100644
--- a/tests/test_sigproc.py
+++ b/tests/test_sigproc.py
@@ -30,6 +30,7 @@ def quantize(q, s):
     expected = q.symbols[index]
     assert r == expected
 
+
 def test_overflow():
     q = sigproc.QAM(config.symbols)
     r = np.random.RandomState(seed=0)
@@ -37,6 +38,7 @@ def test_overflow():
         s = 10*(r.normal() + 1j * r.normal())
         quantize(q, s)
 
+
 def test_linreg():
     x = np.array([1, 3, 2, 8, 4, 6, 9, 7, 0, 5])
     a, b = 12.3, 4.56
@@ -55,22 +57,32 @@ def test_filter():
     y = sigproc.lfilter(b=[0.5], a=[1, -0.5], x=x)
     assert list(y) == [0.5 ** (i+1) for i in range(len(x))]
 
+
 def test_estimate():
     r = np.random.RandomState(seed=0)
     x = r.uniform(-1, 1, [1000])
     x[:10] = 0
     x[len(x)-10:] = 0
 
+    c = 1.23
+    y = c * x
+    c_, = sigproc.estimate(x=x, y=y, order=1)
+    assert abs(c - c_) < 1e-12
+
+    h = [1, 1]
+    y = sigproc.lfilter(b=h, a=[1], x=x)
+    h_ = sigproc.estimate(x=x, y=y, order=len(h))
+    assert norm(h - h_) < 1e-12
+
     h = [0.1, 0.6, 0.9, 0.7, -0.2]
-    L = len(h) / 2
+    L = len(h) // 2
 
     y = sigproc.lfilter(b=h, a=[1], x=x)
     h_ = sigproc.estimate(
         x=x[:len(x)-L], y=y[L:],
         order=len(h), lookahead=L
     )
-    y_ = sigproc.lfilter(b=h_, a=[1], x=x)
-
-    assert norm(y - y_) < 1e-12
     assert norm(h - h_) < 1e-12
 
+    y_ = sigproc.lfilter(b=h_, a=[1], x=x)
+    assert norm(y - y_) < 1e-12