diff --git a/MANIFEST b/MANIFEST
index e49d535..dd17fe8 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -1,5 +1,4 @@
 # file GENERATED by distutils, do NOT edit
-README
 setup.py
 ./src/permanent.c
 permanent/__init__.py
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..24ce15a
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1 @@
+numpy
diff --git a/setup.py b/setup.py
index 60c5546..77f0586 100644
--- a/setup.py
+++ b/setup.py
@@ -3,19 +3,20 @@
 from distutils.core import setup, Extension
 import numpy
 
-setup(name             = "permanent",
-      version          = "0.1.3",
-      description      = "Calculates the permanent of a Numpy matrix",
-      author           = "Pete Shadbolt",
-      author_email     = "pete.shadbolt@gmail.com",
-      maintainer       = "pete.shadbolt@gmail.com",
-      url              = "https://github.com/peteshadbolt/permanent",
-      packages         = ["permanent"],
-      ext_modules      = [
-          Extension(
-              'permanent.permanent', ['./src/permanent.c'],
-              extra_compile_args=["-Ofast", "-march=native"],
-              include_dirs=[numpy.get_include()]),
-      ], 
-      
+setup(
+    name="permanent",
+    version="0.1.3",
+    description="Calculates the permanent of a Numpy matrix",
+    author="Pete Shadbolt",
+    author_email="hello@peteshadbolt.co.uk",
+    maintainer="hello@peteshadbolt.co.uk",
+    url="https://github.com/peteshadbolt/permanent",
+    packages=["permanent"],
+    setup_requires=["numpy"],
+    ext_modules=[
+        Extension(
+            'permanent.permanent', ['./src/permanent.c'],
+            extra_compile_args=["-Ofast", "-march=native"],
+            include_dirs=[numpy.get_include()]),
+    ],
 )
diff --git a/src/permanent.c b/src/permanent.c
index 8479459..781d90b 100644
--- a/src/permanent.c
+++ b/src/permanent.c
@@ -14,12 +14,32 @@ static PyMethodDef methods[] = {
   { NULL, NULL, 0, NULL } // Sentinel
 };
 
-// Module initialization
+
+#if PY_MAJOR_VERSION >= 3
+static struct PyModuleDef cModPyDem =
+{
+    PyModuleDef_HEAD_INIT,
+    "permanent", "Computes the permanent of a numpy using the most appropriate method available",
+    -1,
+    methods
+};
+
+PyMODINIT_FUNC
+PyInit_permanent(void)
+{
+    import_array();
+    return PyModule_Create(&cModPyDem);
+}
+
+#else
+
 PyMODINIT_FUNC initpermanent(void) {                            
   (void) Py_InitModule("permanent", methods);
   import_array();
 }
 
+#endif
+
 // Ryser's algorithm 
 static npy_complex128 ryser(PyArrayObject *submatrix) {
     int n = (int) PyArray_DIM(submatrix, 0);
diff --git a/tests/test_permanent.py b/tests/test_permanent.py
new file mode 100644
index 0000000..5d2787b
--- /dev/null
+++ b/tests/test_permanent.py
@@ -0,0 +1,27 @@
+import numpy as np
+from permanent.permanent import permanent
+import pytest
+
+
+def test_permanent():
+    """ Test that basic functions work right """
+    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)
+
+
+def test_error():
+    """ Should raise a TypeError as we are using the wrong dtype """
+    with pytest.raises(TypeError):
+        m = np.eye(10, dtype=float)
+        permanent(m)
diff --git a/tox.ini b/tox.ini
new file mode 100644
index 0000000..227b948
--- /dev/null
+++ b/tox.ini
@@ -0,0 +1,9 @@
+[tox]
+envlist = py27, py36
+
+[testenv]
+deps=
+    -r requirements.txt
+    pytest
+    pytest-mock
+commands=pytest {posargs}