EIP-96: Add BLOCKHASH contract tests

EIPS/eip-96/tests/.gitignore

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+/*.egg-info/
+/.cache/
+/__pycache__/

EIPS/eip-96/tests/README.md

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+### Usage
+
+1. Setup virtualenv
+2. `pip install -r requirements.txt`
+3. `py.test`

EIPS/eip-96/tests/requirements.txt

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+six
+pytest
+ethereum==1.6.1

EIPS/eip-96/tests/test_blockhash_contract.py

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+import pytest
+import os
+from ethereum import tester, utils
+from ethereum.config import default_config
+from rlp.utils import decode_hex
+
+from pprint import pprint
+
+EIP_BLOCKHASH_CODE = decode_hex(
+    b'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'  # noqa
+)
+
+BLOCKHASH_ADDR = decode_hex(b'00000000000000000000000000000000000000f0')
+EIP_SYSTEM_ADDR = decode_hex(b'fffffffffffffffffffffffffffffffffffffffe')
+
+SYSTEM_PRIV = os.urandom(32)
+SYSTEM_ADDR = utils.privtoaddr(SYSTEM_PRIV)
+SYSTEM_GAS_LIMIT = 1000000
+SYSTEM_GAS_PRICE = 0
+BLOCKHASH_CODE = EIP_BLOCKHASH_CODE.replace(EIP_SYSTEM_ADDR, SYSTEM_ADDR, 1)
+NULL_HASH = b'\0' * 32
+
+# Configure execution in pre-Metropolis mode.
+default_config['HOMESTEAD_FORK_BLKNUM'] = 0
+default_config['DAO_FORK_BLKNUM'] = 0
+default_config['ANTI_DOS_FORK_BLKNUM'] = 0
+default_config['CLEARING_FORK_BLKNUM'] = 0
+
+
+class State(tester.state):
+    def exec_system(self):
+        """Execute BLOCKHASH contract from SYSTEM account"""
+
+        prev_block_hash = self.block.get_parent().hash
+        assert len(prev_block_hash) == 32
+
+        gas_limit = tester.gas_limit
+        tester.gas_limit = SYSTEM_GAS_LIMIT
+
+        gas_price = tester.gas_price
+        tester.gas_price = SYSTEM_GAS_PRICE
+
+        output = self.send(sender=SYSTEM_PRIV, to=BLOCKHASH_ADDR, value=0,
+                           evmdata=prev_block_hash)
+        assert len(output) == 0
+
+        tester.gas_limit = gas_limit
+        tester.gas_price = gas_price
+
+    def get_slot(self, index):
+        """Get storage entry of BLOCKHASH_ADDR of given index"""
+        int_value = self.block.get_storage_data(BLOCKHASH_ADDR, index)
+        return utils.zpad(utils.coerce_to_bytes(int_value), 32)
+
+
+@pytest.fixture(scope='module')
+def state():
+    state = State()
+    state.block._set_acct_item(BLOCKHASH_ADDR, 'code', BLOCKHASH_CODE)
+
+    for i in range(257):
+        state.mine()
+        state.exec_system()
+
+    return state
+
+
+def test_setup(state):
+    assert state.block.get_code(BLOCKHASH_ADDR) == BLOCKHASH_CODE
+    assert state.block.get_balance(SYSTEM_ADDR) == 0
+    assert state.block.get_nonce(SYSTEM_ADDR) > 0
+
+    assert state.get_slot(0) == state.blocks[256].hash
+    for i in range(1, 256):
+        assert state.get_slot(i) == state.blocks[i].hash
+
+    assert state.get_slot(256) == state.blocks[0].hash
+    assert state.get_slot(257) == state.blocks[256].hash
+    for i in range(258, 256 + 256):
+        assert state.get_slot(i) == NULL_HASH
+
+    assert state.get_slot(512) == state.blocks[0].hash
+    for i in range(513, 512 + 256):
+        assert state.get_slot(i) == NULL_HASH
+
+
+def test_get_prev_block_hash(state):
+    prev = state.block.number - 1
+    pprint(prev)
+    expected_hash = state.blocks[prev].hash
+    arg = utils.zpad(utils.coerce_to_bytes(prev), 32)
+    out = state.profile(sender=tester.k1, to=BLOCKHASH_ADDR, value=0,
+                        evmdata=arg)
+    assert out['output'] == expected_hash
+    assert out['gas'] == 330
+
+
+def test_get_current_block_hash(state):
+    arg = utils.zpad(utils.coerce_to_bytes(state.block.number), 32)
+    out = state.profile(sender=tester.k1, to=BLOCKHASH_ADDR, value=0,
+                        evmdata=arg)
+    assert out['output'] == b'\0' * 32
+    assert out['gas'] == 79
+
+
+def test_get_future_block_hash(state):
+    arg = utils.zpad(utils.coerce_to_bytes(3**11 + 13), 32)
+    out = state.profile(sender=tester.k1, to=BLOCKHASH_ADDR, value=0,
+                        evmdata=arg)
+    assert out['output'] == b'\0' * 32
+    assert out['gas'] == 79
+
+
+def test_first256th_slot(state):
+    n = state.block.number
+    state.block.number = 60000  # Allow accessing 256th block hashes
+
+    arg = utils.zpad(utils.coerce_to_bytes(0), 32)
+    out = state.profile(sender=tester.k1, to=BLOCKHASH_ADDR, value=0,
+                        evmdata=arg)
+    assert out['output'] == state.blocks[0].hash
+    assert out['gas'] == 429
+
+    state.block.number = n