EIP-96: Add overflow tests for argument check

EIPS/eip-96/tests/test_blockhash_contract.py

@@ -150,12 +150,35 @@ def test_first256th_slot(state):
     state.block.number = n
 
 
+def test_overflow(state):
+    n = state.block.number
+    state.block.number = 1
+
+    arg = utils.zpad(utils.coerce_to_bytes(2**256 - 256), 32)
+    out = state.profile(sender=tester.k1, to=BLOCKHASH_ADDR, value=0,
+                        evmdata=arg)
+    assert out['output'] == NULL_HASH
+    assert out['gas'] == 79
+
+    state.block.number = n
+
+
 def test_fake_state_setup(fake_state):
     for i in range(3 * 256):
         assert fake_state.get_slot(i) == fake_slot(i)
     assert fake_state.get_slot(3 * 256) == NULL_HASH
 
 
+def test_overflow2(fake_state):
+    fake_state.block.number = 255
+
+    arg = '\xff' * 31
+    out = fake_state.profile(sender=tester.k1, to=BLOCKHASH_ADDR, value=0,
+                             evmdata=arg)
+    assert out['output'] == NULL_HASH
+    assert out['gas'] == 79
+
+
 def test_blockhash_last256(fake_state):
     start_block = fake_state.block.number - 256
     for n in range(start_block, fake_state.block.number):