diff --git a/run-tests.py b/run-tests.py
deleted file mode 100644
index 8c65608..0000000
--- a/run-tests.py
+++ /dev/null
@@ -1,42 +0,0 @@
-import os, sys
-import numpy as np
-import time
-from matplotlib import pyplot as plt
-from permanent import permanent
-import itertools as it
-
-
-def permanent(a):
-    """ Slow way to compute the permanent """
-    r = range(len(a))
-    return sum([np.prod(a[r, p]) for p in it.permutations(r)])
-
-
-if __name__ == '__main__':
-    maxtime=1
-    dimensions=range(1,11)
-
-    for (function, label) in zip((permanent, perm_ryser), ("C", "Python")):
-        counts=[]
-        for dimension in dimensions:
-            print dimension
-            real=np.random.uniform(-1, 1, dimension*dimension).reshape((dimension, dimension))
-            imag=np.random.uniform(-1, 1, dimension*dimension).reshape((dimension, dimension))
-            submatrix=real+1j*imag
-
-            t=time.clock()
-            n=0
-            while time.clock()-t < maxtime:
-                for i in range(5):
-                    function(submatrix)
-                n+=5
-            counts.append(n)
-
-        plt.plot(dimensions, counts, ".-", label=label)
-
-    plt.ylabel("Number of permanents per second")
-    plt.xlabel("Dimension")
-    plt.xlim(min(dimensions), max(dimensions))
-    plt.legend()
-    plt.semilogy()
-    plt.savefig("out.pdf")
diff --git a/run-tests.sh b/run-tests.sh
deleted file mode 100755
index 19b6c35..0000000
--- a/run-tests.sh
+++ /dev/null
@@ -1,5 +0,0 @@
-#!/bin/bash
-
-rm permanent/*.so
-python ./setup.py build_ext --inplace &&
-python ./run-tests.py
diff --git a/src/permanent.c b/src/permanent.c
index 0093f7d..8479459 100644
--- a/src/permanent.c
+++ b/src/permanent.c
@@ -48,6 +48,10 @@ static PyObject *permanent(PyObject *self, PyObject *args) {
   // Parse the input
   PyArrayObject *submatrix;
   if (!PyArg_ParseTuple(args, "O!", &PyArray_Type, &submatrix)) {return NULL;}
+  if (!PyArray_ISCOMPLEX(submatrix)) {
+      PyErr_SetString(PyExc_TypeError, "Array dtype must be `complex`.");
+      return NULL;
+  }
 
   // Compute the permanent
   npy_complex128 p = ryser(submatrix);
diff --git a/tests/test.py b/tests/test.py
new file mode 100644
index 0000000..229ff2f
--- /dev/null
+++ b/tests/test.py
@@ -0,0 +1,27 @@
+import numpy as np
+from permanent import permanent
+from nose.tools import raises
+
+def test_permanent():
+    """ Dumb tests """
+    m = np.eye(10, dtype=complex)
+    assert permanent(m) == 1
+    m = np.zeros((10, 10), dtype=complex)
+    assert permanent(m) == 0
+
+
+def test_floaty():
+    """ More tests using a precomputed permanent """
+    np.random.seed(1234)
+    m = np.random.uniform(0, 1, 16) + 1j*np.random.uniform(0, 1, 16)
+    m = m.reshape(4,4)
+    p = permanent(m)
+    assert np.allclose(p, -8.766131870776363+1.072095650303524j)
+
+    
+@raises(TypeError)
+def test_error():
+    """ Should raise a TypeError as we are using the wrong dtype """
+    m = np.eye(10, dtype=float)
+    permanent(m)
+