add UT for ECC failure

amodem/ecc.py

@@ -42,7 +42,6 @@ def decode(blocks, nsym=DEFAULT_NSYM):
 
         size = chunk[0]
         payload = chunk[1:]
-        if size > len(payload):
-            raise ValueError('Invalid chunk', size, len(payload), payload)
+        assert size <= len(payload)
 
         yield payload[:size]

tests/test_ecc.py

@@ -1,6 +1,7 @@
 from amodem import ecc
 import random
 import itertools
+import reedsolo
 
 
 def concat(chunks):
@@ -13,3 +14,19 @@ def test_random():
     y = ecc.encode(x)
     x_ = concat(ecc.decode(y))
     assert x_ == x
+
+
+def test_errors():
+    data = bytearray(range(244))
+    blocks = list(ecc.encode(data))
+    assert len(blocks) == 2
+    for i in range(ecc.DEFAULT_NSYM/2):
+        blocks[0][i] = blocks[0][i] ^ 0xFF
+
+    i = ecc.DEFAULT_NSYM/2
+    try:
+        blocks[0][i] = blocks[0][i] ^ 0xFF
+        concat(ecc.decode(blocks))
+        assert False
+    except reedsolo.ReedSolomonError as e:
+        assert e.args == ('Too many errors to correct',)