Add test for sampling

sampling.py

@@ -25,10 +25,10 @@ class Interpolator(object):
         return coeffs, k - self.width
 
 class Sampler(object):
-    def __init__(self, src, interp):
+    def __init__(self, src, interp=None):
         self.src = iter(src)
         self.freq = 1.0
-        self.interp = interp
+        self.interp = interp if (interp is not None) else Interpolator()
         coeffs, begin = self.interp.get(0)
         self.offset = -begin  # should fill samples buffer
         self.buff = np.zeros(len(coeffs))

test_sampling.py

@@ -0,0 +1,12 @@
+import sampling
+import numpy as np
+
+def test_resample():
+    x = np.arange(300)
+    s = sampling.Sampler(x)
+    y = np.array(list(s))
+
+    k = s.interp.width - 1
+    x = x[k:-k-1]
+    err = np.max(np.abs(x - y))
+    assert err < 1e-10