Add pairwise swap challenge

bit_manipulation/pairwise_swap/test_pairwise_swap.py

@@ -0,0 +1,24 @@
+from nose.tools import assert_equal, assert_raises
+
+
+class TestBits(object):
+
+    def test_pairwise_swap(self):
+        bits = Bits()
+        assert_equal(bits.pairwise_swap(0), 0)
+        assert_equal(bits.pairwise_swap(1), 1)
+        num = int('0000100111110110', base=2)
+        expected = int('0000011011111001', base=2)
+        assert_equal(bits.pairwise_swap(num), expected)
+        assert_raises(TypeError, bits.pairwise_swap, None)
+        
+        print('Success: test_pairwise_swap')
+
+
+def main():
+    test = TestBits()
+    test.test_pairwise_swap()
+
+
+if __name__ == '__main__':
+    main()