Add CScriptOp.(encode|decode)_op_n() unit tests

Fixed a few uncovered bugs

Author: petertodd

bitcoin/script.py

@@ -52,13 +52,13 @@ def encode_op_n(n):
         if n == 0:
             return OP_0
         else:
-            return OP_1 + n-1
+            return CScriptOp(OP_1 + n-1)
 
     def decode_op_n(self):
         if self == OP_0:
             return 0
 
-        if not (OP_0 <= self <= OP_16):
+        if not (self == OP_0 or OP_1 <= self <= OP_16):
             raise ValueError('op %r is not an OP_N' % self)
 
         return int(self - OP_1+1)

bitcoin/tests/test_script.py

@@ -39,6 +39,40 @@ def test_is_singleton(self):
         for i in range(0x0, 0x100):
             self.assertTrue(CScriptOp(i) is CScriptOp(i))
 
+    def test_encode_decode_op_n(self):
+        def t(n, op):
+            actual = CScriptOp.encode_op_n(n)
+            self.assertEqual(actual, op)
+            self.assertTrue(isinstance(actual, CScriptOp))
+
+            actual = op.decode_op_n()
+            self.assertEqual(actual, n)
+            self.assertTrue(isinstance(actual, int))
+
+        t(0, OP_0)
+        t(1, OP_1)
+        t(2, OP_2)
+        t(3, OP_3)
+        t(4, OP_4)
+        t(5, OP_5)
+        t(6, OP_6)
+        t(7, OP_7)
+        t(8, OP_8)
+        t(9, OP_9)
+        t(9, OP_9)
+        t(10, OP_10)
+        t(11, OP_11)
+        t(12, OP_12)
+        t(13, OP_13)
+        t(14, OP_14)
+        t(15, OP_15)
+        t(16, OP_16)
+
+        with self.assertRaises(ValueError):
+            OP_CHECKSIG.decode_op_n()
+
+        with self.assertRaises(ValueError):
+            CScriptOp(1).decode_op_n()
 
 class Test_CScript(unittest.TestCase):
     def test_tokenize_roundtrip(self):