diff --git a/aprs/version.py b/aprs/version.py
index e2f45ae..7c9e66e 100644
--- a/aprs/version.py
+++ b/aprs/version.py
@@ -1 +1 @@
-__version__ = '0.6.5'
+__version__ = '0.6.6'
diff --git a/run_tests.sh b/run_tests.sh
new file mode 100755
index 0000000..698324f
--- /dev/null
+++ b/run_tests.sh
@@ -0,0 +1,3 @@
+#!/bin/bash
+
+python -m unittest discover -v -s tests
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_base91.py b/tests/test_base91.py
new file mode 100644
index 0000000..e91861c
--- /dev/null
+++ b/tests/test_base91.py
@@ -0,0 +1,106 @@
+import unittest
+
+from aprs import base91
+
+
+class a_FromDecimal(unittest.TestCase):
+    def test_valid_input(self):
+        testData = [
+            [0, '!'],
+            [1, '"'],
+            [90, '{'],
+            [91, '"!'],
+            ]
+
+        # 91**1 = "!
+        # 91**2 = "!!
+        # 91**3 = "!!!
+        # etc
+        testData += [[91**i, '"' + '!'*i] for i in xrange(20)]
+
+        for n, expected in testData:
+            self.assertEqual(expected, base91.from_decimal(n))
+
+    def test_invalid_input_type(self):
+        testData = ['0', '1', 1.0, None, [0]]
+
+        for n in testData:
+            self.assertRaises(ValueError, base91.from_decimal, n)
+
+    def test_invalid_input_range(self):
+        testData = [-10000, -5, -1]
+
+        for n in testData:
+            self.assertRaises(ValueError, base91.from_decimal, n)
+
+    def test_valid_padding(self):
+        testData = [1, 2, 5, 10, 100]
+
+        for n in testData:
+            self.assertEqual(n, len(base91.from_decimal(0, n)))
+
+    def test_invalid_padding(self):
+        testData = [0, -1, -100]
+
+        for n in testData:
+            self.assertRaises(ValueError, base91.from_decimal, 0, padding=n)
+
+
+class b_ToDecimal(unittest.TestCase):
+    def test_valid_input(self):
+        testData = [
+            [0, '!'],
+            [0, '!!!!!!!!!'],
+            [1, '"'],
+            [1, '!!"'],
+            [90, '{'],
+            [90, '!{'],
+            [91, '"!'],
+            [91, '!!!"!'],
+            ]
+
+        # 91**1 = "!
+        # 91**2 = "!!
+        # 91**3 = "!!!
+        # etc
+        testData += [[91**i, '"' + '!'*i] for i in xrange(20)]
+
+        for expected, n in testData:
+            self.assertEqual(expected, base91.to_decimal(n))
+
+    def test_invalid_input_type(self):
+        testData = [-1, 0, 5, unicode('a'), None, ['d']]
+
+        for n in testData:
+            self.assertRaises(TypeError, base91.to_decimal, n)
+
+    def test_invalid_input(self):
+        # test for every value outside of the accepted range
+        testData = [chr(i) for i in range(ord('!'))+range(ord('{')+1, 256)]
+
+        # same as above, except each value is prefix with a valid char
+        testData += ['!'+c for c in testData]
+
+        for n in testData:
+            self.assertRaises(ValueError, base91.to_decimal, n)
+
+
+class c_Both(unittest.TestCase):
+    def test_from_decimal_to_decimal(self):
+        for number in xrange(91**2 + 5):
+            text = base91.from_decimal(number)
+            result = base91.to_decimal(text)
+
+            self.assertEqual(result, number)
+
+    def test_stability(self):
+        for number in xrange(50):
+            largeN = 91 ** number
+            text = base91.from_decimal(largeN)
+            result = base91.to_decimal(text)
+
+            self.assertEqual(result, largeN)
+
+
+if __name__ == '__main__':
+    unittest.main()