Add test for sampling

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