Add comparison tool test runner, built on mininode

comptool.py creates a tool for running a test suite on top of the mininode p2p
framework.  It supports two types of tests: those for which we expect certain
behavior (acceptance or rejection of a block or transaction) and those for
which we are just comparing that the behavior of 2 or more nodes is the same.

blockstore.py defines BlockStore and TxStore, which provide db-backed maps
between block/tx hashes and the corresponding block or tx.

blocktools.py defines utility functions for creating and manipulating blocks
and transactions.

invalidblockrequest.py is an example test in the comptool framework, which
tests the behavior of a single node when sent two different types of invalid
blocks (a block with a duplicated transaction and a block with a bad coinbase
value).

6 files changed, 667 insertions, 0 deletions

diff --git a/qa/pull-tester/rpc-tests.sh b/qa/pull-tester/rpc-tests.sh
index 6d57d58755..ae27a94b8d 100755
--- a/qa/pull-tester/rpc-tests.sh
+++ b/qa/pull-tester/rpc-tests.sh
@@ -31,6 +31,7 @@ testScripts=(
     'merkle_blocks.py'
 #    'forknotify.py'
     'maxblocksinflight.py'
+    'invalidblockrequest.py'
 );
 if [ "x${ENABLE_BITCOIND}${ENABLE_UTILS}${ENABLE_WALLET}" = "x111" ]; then
     for (( i = 0; i < ${#testScripts[@]}; i++ ))
diff --git a/qa/rpc-tests/blockstore.py b/qa/rpc-tests/blockstore.py
new file mode 100644
index 0000000000..c57b6df81b
--- /dev/null
+++ b/qa/rpc-tests/blockstore.py
@@ -0,0 +1,127 @@
+# BlockStore: a helper class that keeps a map of blocks and implements
+#             helper functions for responding to getheaders and getdata,
+#             and for constructing a getheaders message
+#
+
+from mininode import *
+import dbm
+
+class BlockStore(object):
+    def __init__(self, datadir):
+        self.blockDB = dbm.open(datadir + "/blocks", 'c')
+        self.currentBlock = 0L
+    
+    def close(self):
+        self.blockDB.close()
+
+    def get(self, blockhash):
+        serialized_block = None
+        try:
+            serialized_block = self.blockDB[repr(blockhash)]
+        except KeyError:
+            return None
+        f = cStringIO.StringIO(serialized_block)
+        ret = CBlock()
+        ret.deserialize(f)
+        ret.calc_sha256()
+        return ret
+
+    # Note: this pulls full blocks out of the database just to retrieve
+    # the headers -- perhaps we could keep a separate data structure
+    # to avoid this overhead.
+    def headers_for(self, locator, hash_stop, current_tip=None):
+        if current_tip is None:
+            current_tip = self.currentBlock
+        current_block = self.get(current_tip)
+        if current_block is None:
+            return None
+
+        response = msg_headers()
+        headersList = [ CBlockHeader(current_block) ]
+        maxheaders = 2000
+        while (headersList[0].sha256 not in locator.vHave):
+            prevBlockHash = headersList[0].hashPrevBlock
+            prevBlock = self.get(prevBlockHash)
+            if prevBlock is not None:
+                headersList.insert(0, CBlockHeader(prevBlock))
+            else:
+                break
+        headersList = headersList[:maxheaders] # truncate if we have too many
+        hashList = [x.sha256 for x in headersList]
+        index = len(headersList)
+        if (hash_stop in hashList):
+            index = hashList.index(hash_stop)+1
+        response.headers = headersList[:index]
+        return response
+
+    def add_block(self, block):
+        block.calc_sha256()
+        try:
+            self.blockDB[repr(block.sha256)] = bytes(block.serialize())
+        except TypeError as e:
+            print "Unexpected error: ", sys.exc_info()[0], e.args
+        self.currentBlock = block.sha256
+
+    def get_blocks(self, inv):
+        responses = []
+        for i in inv:
+            if (i.type == 2): # MSG_BLOCK
+                block = self.get(i.hash)
+                if block is not None:
+                    responses.append(msg_block(block))
+        return responses
+
+    def get_locator(self, current_tip=None):
+        if current_tip is None:
+            current_tip = self.currentBlock
+        r = []
+        counter = 0
+        step = 1
+        lastBlock = self.get(current_tip)
+        while lastBlock is not None:
+            r.append(lastBlock.hashPrevBlock)
+            for i in range(step):
+                lastBlock = self.get(lastBlock.hashPrevBlock)
+                if lastBlock is None:
+                    break
+            counter += 1
+            if counter > 10:
+                step *= 2
+        locator = CBlockLocator()
+        locator.vHave = r
+        return locator
+
+class TxStore(object):
+    def __init__(self, datadir):
+        self.txDB = dbm.open(datadir + "/transactions", 'c')
+
+    def close(self):
+        self.txDB.close()
+
+    def get(self, txhash):
+        serialized_tx = None
+        try:
+            serialized_tx = self.txDB[repr(txhash)]
+        except KeyError:
+            return None
+        f = cStringIO.StringIO(serialized_tx)
+        ret = CTransaction()
+        ret.deserialize(f)
+        ret.calc_sha256()
+        return ret
+
+    def add_transaction(self, tx):
+        tx.calc_sha256()
+        try:
+            self.txDB[repr(tx.sha256)] = bytes(tx.serialize())
+        except TypeError as e:
+            print "Unexpected error: ", sys.exc_info()[0], e.args
+
+    def get_transactions(self, inv):
+        responses = []
+        for i in inv:
+            if (i.type == 1): # MSG_TX
+                tx = self.get(i.hash)
+                if tx is not None:
+                    responses.append(msg_tx(tx))
+        return responses
diff --git a/qa/rpc-tests/blocktools.py b/qa/rpc-tests/blocktools.py
new file mode 100644
index 0000000000..f397fe7cd6
--- /dev/null
+++ b/qa/rpc-tests/blocktools.py
@@ -0,0 +1,65 @@
+# blocktools.py - utilities for manipulating blocks and transactions
+#
+# Distributed under the MIT/X11 software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+#
+
+from mininode import *
+from script import CScript, CScriptOp
+
+# Create a block (with regtest difficulty)
+def create_block(hashprev, coinbase, nTime=None):
+    block = CBlock()
+    if nTime is None:
+        import time
+        block.nTime = int(time.time()+600)
+    else:
+        block.nTime = nTime
+    block.hashPrevBlock = hashprev
+    block.nBits = 0x207fffff # Will break after a difficulty adjustment...
+    block.vtx.append(coinbase)
+    block.hashMerkleRoot = block.calc_merkle_root()
+    block.calc_sha256()
+    return block
+
+def serialize_script_num(value):
+    r = bytearray(0)
+    if value == 0:
+        return r
+    neg = value < 0
+    absvalue = -value if neg else value
+    while (absvalue):
+        r.append(chr(absvalue & 0xff))
+        absvalue >>= 8
+    if r[-1] & 0x80:
+        r.append(0x80 if neg else 0)
+    elif neg:
+        r[-1] |= 0x80
+    return r
+
+counter=1
+# Create an anyone-can-spend coinbase transaction, assuming no miner fees
+def create_coinbase(heightAdjust = 0):
+    global counter
+    coinbase = CTransaction()
+    coinbase.vin.append(CTxIn(COutPoint(0, 0xffffffff), 
+                ser_string(serialize_script_num(counter+heightAdjust)), 0xffffffff))
+    counter += 1
+    coinbaseoutput = CTxOut()
+    coinbaseoutput.nValue = 50*100000000
+    halvings = int((counter+heightAdjust)/150) # regtest
+    coinbaseoutput.nValue >>= halvings
+    coinbaseoutput.scriptPubKey = ""
+    coinbase.vout = [ coinbaseoutput ]
+    coinbase.calc_sha256()
+    return coinbase
+
+# Create a transaction with an anyone-can-spend output, that spends the
+# nth output of prevtx.
+def create_transaction(prevtx, n, sig, value):
+    tx = CTransaction()
+    assert(n < len(prevtx.vout))
+    tx.vin.append(CTxIn(COutPoint(prevtx.sha256, n), sig, 0xffffffff))
+    tx.vout.append(CTxOut(value, ""))
+    tx.calc_sha256()
+    return tx
diff --git a/qa/rpc-tests/comptool.py b/qa/rpc-tests/comptool.py
new file mode 100755
index 0000000000..6125bae51e
--- /dev/null
+++ b/qa/rpc-tests/comptool.py
@@ -0,0 +1,330 @@
+#!/usr/bin/env python2
+#
+# Distributed under the MIT/X11 software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+#
+
+from mininode import *
+from blockstore import BlockStore, TxStore
+from util import p2p_port
+
+'''
+This is a tool for comparing two or more bitcoinds to each other
+using a script provided.
+
+To use, create a class that implements get_tests(), and pass it in
+as the test generator to TestManager.  get_tests() should be a python
+generator that returns TestInstance objects.  See below for definition.
+'''
+
+# TestNode behaves as follows:
+# Configure with a BlockStore and TxStore
+# on_inv: log the message but don't request
+# on_headers: log the chain tip
+# on_pong: update ping response map (for synchronization)
+# on_getheaders: provide headers via BlockStore
+# on_getdata: provide blocks via BlockStore
+
+class TestNode(NodeConnCB):
+
+    def __init__(self, block_store, tx_store):
+        NodeConnCB.__init__(self)
+        self.create_callback_map()
+        self.conn = None
+        self.bestblockhash = None
+        self.block_store = block_store
+        self.block_request_map = {}
+        self.tx_store = tx_store
+        self.tx_request_map = {}
+
+        # When the pingmap is non-empty we're waiting for 
+        # a response
+        self.pingMap = {} 
+        self.lastInv = []
+
+    def add_connection(self, conn):
+        self.conn = conn
+
+    def on_headers(self, conn, message):
+        if len(message.headers) > 0:
+            best_header = message.headers[-1]
+            best_header.calc_sha256()
+            self.bestblockhash = best_header.sha256
+
+    def on_getheaders(self, conn, message):
+        response = self.block_store.headers_for(message.locator, message.hashstop)
+        if response is not None:
+            conn.send_message(response)
+
+    def on_getdata(self, conn, message):
+        [conn.send_message(r) for r in self.block_store.get_blocks(message.inv)]
+        [conn.send_message(r) for r in self.tx_store.get_transactions(message.inv)]
+
+        for i in message.inv:
+            if i.type == 1:
+                self.tx_request_map[i.hash] = True
+            elif i.type == 2:
+                self.block_request_map[i.hash] = True
+
+    def on_inv(self, conn, message):
+        self.lastInv = [x.hash for x in message.inv]
+
+    def on_pong(self, conn, message):
+        try:
+            del self.pingMap[message.nonce]
+        except KeyError:
+            raise AssertionError("Got pong for unknown ping [%s]" % repr(message))
+
+    def send_inv(self, obj):
+        mtype = 2 if isinstance(obj, CBlock) else 1
+        self.conn.send_message(msg_inv([CInv(mtype, obj.sha256)]))
+
+    def send_getheaders(self):
+        # We ask for headers from their last tip.
+        m = msg_getheaders()
+        m.locator = self.block_store.get_locator(self.bestblockhash)
+        self.conn.send_message(m)
+
+    # This assumes BIP31
+    def send_ping(self, nonce):
+        self.pingMap[nonce] = True
+        self.conn.send_message(msg_ping(nonce))
+
+    def received_ping_response(self, nonce):
+        return nonce not in self.pingMap
+
+    def send_mempool(self):
+        self.lastInv = []
+        self.conn.send_message(msg_mempool())
+
+# TestInstance:
+#
+# Instances of these are generated by the test generator, and fed into the
+# comptool.
+#
+# "blocks_and_transactions" should be an array of [obj, True/False/None]:
+#  - obj is either a CBlock or a CTransaction, and 
+#  - the second value indicates whether the object should be accepted
+#    into the blockchain or mempool (for tests where we expect a certain
+#    answer), or "None" if we don't expect a certain answer and are just
+#    comparing the behavior of the nodes being tested.
+# sync_every_block: if True, then each block will be inv'ed, synced, and
+#    nodes will be tested based on the outcome for the block.  If False,
+#    then inv's accumulate until all blocks are processed (or max inv size
+#    is reached) and then sent out in one inv message.  Then the final block
+#    will be synced across all connections, and the outcome of the final 
+#    block will be tested.
+# sync_every_tx: analagous to behavior for sync_every_block, except if outcome
+#    on the final tx is None, then contents of entire mempool are compared
+#    across all connections.  (If outcome of final tx is specified as true
+#    or false, then only the last tx is tested against outcome.)
+
+class TestInstance(object):
+    def __init__(self, objects=[], sync_every_block=True, sync_every_tx=False):
+        self.blocks_and_transactions = objects
+        self.sync_every_block = sync_every_block
+        self.sync_every_tx = sync_every_tx
+
+class TestManager(object):
+
+    def __init__(self, testgen, datadir):
+        self.test_generator = testgen
+        self.connections    = []
+        self.block_store    = BlockStore(datadir)
+        self.tx_store       = TxStore(datadir)
+        self.ping_counter   = 1
+
+    def add_all_connections(self, nodes):
+        for i in range(len(nodes)):
+            # Create a p2p connection to each node
+            self.connections.append(NodeConn('127.0.0.1', p2p_port(i), 
+                        nodes[i], TestNode(self.block_store, self.tx_store)))
+            # Make sure the TestNode (callback class) has a reference to its
+            # associated NodeConn
+            self.connections[-1].cb.add_connection(self.connections[-1])
+
+    def wait_for_verack(self):
+        sleep_time = 0.05
+        max_tries = 10 / sleep_time  # Wait at most 10 seconds
+        while max_tries > 0:
+            done = True
+            for c in self.connections:
+                if c.cb.verack_received is False:
+                    done = False
+                    break
+            if done:
+                break
+            time.sleep(sleep_time)
+
+    def wait_for_pings(self, counter):
+        received_pongs = False
+        while received_pongs is not True:
+            time.sleep(0.05)
+            received_pongs = True
+            for c in self.connections:
+                if c.cb.received_ping_response(counter) is not True:
+                    received_pongs = False
+                    break
+
+    # sync_blocks: Wait for all connections to request the blockhash given
+    # then send get_headers to find out the tip of each node, and synchronize
+    # the response by using a ping (and waiting for pong with same nonce).
+    def sync_blocks(self, blockhash, num_blocks):
+        # Wait for nodes to request block (50ms sleep * 20 tries * num_blocks)
+        max_tries = 20*num_blocks
+        while max_tries > 0:
+            results = [ blockhash in c.cb.block_request_map and
+                        c.cb.block_request_map[blockhash] for c in self.connections ]
+            if False not in results:
+                break
+            time.sleep(0.05)
+            max_tries -= 1
+
+        # --> error if not requested
+        if max_tries == 0:
+            # print [ c.cb.block_request_map for c in self.connections ]
+            raise AssertionError("Not all nodes requested block")
+        # --> Answer request (we did this inline!)
+
+        # Send getheaders message
+        [ c.cb.send_getheaders() for c in self.connections ]
+
+        # Send ping and wait for response -- synchronization hack
+        [ c.cb.send_ping(self.ping_counter) for c in self.connections ]
+        self.wait_for_pings(self.ping_counter)
+        self.ping_counter += 1
+
+    # Analogous to sync_block (see above)
+    def sync_transaction(self, txhash, num_events):
+        # Wait for nodes to request transaction (50ms sleep * 20 tries * num_events)
+        max_tries = 20*num_events
+        while max_tries > 0:
+            results = [ txhash in c.cb.tx_request_map and
+                        c.cb.tx_request_map[txhash] for c in self.connections ]
+            if False not in results:
+                break
+            time.sleep(0.05)
+            max_tries -= 1
+
+        # --> error if not requested
+        if max_tries == 0:
+            # print [ c.cb.tx_request_map for c in self.connections ]
+            raise AssertionError("Not all nodes requested transaction")
+        # --> Answer request (we did this inline!)
+
+        # Get the mempool
+        [ c.cb.send_mempool() for c in self.connections ]
+
+        # Send ping and wait for response -- synchronization hack
+        [ c.cb.send_ping(self.ping_counter) for c in self.connections ]
+        self.wait_for_pings(self.ping_counter)
+        self.ping_counter += 1
+
+        # Sort inv responses from each node
+        [ c.cb.lastInv.sort() for c in self.connections ]
+
+    # Verify that the tip of each connection all agree with each other, and
+    # with the expected outcome (if given)
+    def check_results(self, blockhash, outcome):
+        for c in self.connections:
+            if outcome is None:
+                if c.cb.bestblockhash != self.connections[0].cb.bestblockhash:
+                    return False
+            elif ((c.cb.bestblockhash == blockhash) != outcome):
+                # print c.cb.bestblockhash, blockhash, outcome
+                return False
+        return True
+
+    # Either check that the mempools all agree with each other, or that
+    # txhash's presence in the mempool matches the outcome specified.
+    # This is somewhat of a strange comparison, in that we're either comparing
+    # a particular tx to an outcome, or the entire mempools altogether;
+    # perhaps it would be useful to add the ability to check explicitly that
+    # a particular tx's existence in the mempool is the same across all nodes.
+    def check_mempool(self, txhash, outcome):
+        for c in self.connections:
+            if outcome is None:
+                # Make sure the mempools agree with each other
+                if c.cb.lastInv != self.connections[0].cb.lastInv:
+                    # print c.rpc.getrawmempool()
+                    return False
+            elif ((txhash in c.cb.lastInv) != outcome):
+                # print c.rpc.getrawmempool(), c.cb.lastInv
+                return False
+        return True
+
+    def run(self):
+        # Wait until verack is received
+        self.wait_for_verack()
+
+        test_number = 1
+        for test_instance in self.test_generator.get_tests():
+            # We use these variables to keep track of the last block
+            # and last transaction in the tests, which are used
+            # if we're not syncing on every block or every tx.
+            [ block, block_outcome ] = [ None, None ]
+            [ tx, tx_outcome ] = [ None, None ]
+            invqueue = []
+
+            for b_or_t, outcome in test_instance.blocks_and_transactions:
+                # Determine if we're dealing with a block or tx
+                if isinstance(b_or_t, CBlock):  # Block test runner
+                    block = b_or_t
+                    block_outcome = outcome
+                    # Add to shared block_store, set as current block
+                    self.block_store.add_block(block)
+                    for c in self.connections:
+                        c.cb.block_request_map[block.sha256] = False
+                    # Either send inv's to each node and sync, or add
+                    # to invqueue for later inv'ing.
+                    if (test_instance.sync_every_block):
+                        [ c.cb.send_inv(block) for c in self.connections ]
+                        self.sync_blocks(block.sha256, 1)
+                        if (not self.check_results(block.sha256, outcome)):
+                            raise AssertionError("Test failed at test %d" % test_number)
+                    else:
+                        invqueue.append(CInv(2, block.sha256))
+                else:  # Tx test runner
+                    assert(isinstance(b_or_t, CTransaction))
+                    tx = b_or_t
+                    tx_outcome = outcome
+                    # Add to shared tx store
+                    self.tx_store.add_transaction(tx)
+                    for c in self.connections:
+                        c.cb.tx_request_map[tx.sha256] = False
+                    # Again, either inv to all nodes or save for later
+                    if (test_instance.sync_every_tx):
+                        [ c.cb.send_inv(tx) for c in self.connections ]
+                        self.sync_transaction(tx.sha256, 1)
+                        if (not self.check_mempool(tx.sha256, outcome)):
+                            raise AssertionError("Test failed at test %d" % test_number)
+                    else:
+                        invqueue.append(CInv(1, tx.sha256))
+                # Ensure we're not overflowing the inv queue
+                if len(invqueue) == MAX_INV_SZ:
+                    [ c.sb.send_message(msg_inv(invqueue)) for c in self.connections ]
+                    invqueue = []
+
+            # Do final sync if we weren't syncing on every block or every tx.
+            if (not test_instance.sync_every_block and block is not None):
+                if len(invqueue) > 0:
+                    [ c.send_message(msg_inv(invqueue)) for c in self.connections ]
+                    invqueue = []
+                self.sync_blocks(block.sha256,
+                                 len(test_instance.blocks_and_transactions))
+                if (not self.check_results(block.sha256, block_outcome)):
+                    raise AssertionError("Block test failed at test %d" % test_number)
+            if (not test_instance.sync_every_tx and tx is not None):
+                if len(invqueue) > 0:
+                    [ c.send_message(msg_inv(invqueue)) for c in self.connections ]
+                    invqueue = []
+                self.sync_transaction(tx.sha256, len(test_instance.blocks_and_transactions))
+                if (not self.check_mempool(tx.sha256, tx_outcome)):
+                    raise AssertionError("Mempool test failed at test %d" % test_number)
+
+            print "Test %d: PASS" % test_number, [ c.rpc.getblockcount() for c in self.connections ]
+            test_number += 1
+
+        self.block_store.close()
+        self.tx_store.close()
+        [ c.disconnect_node() for c in self.connections ]
diff --git a/qa/rpc-tests/invalidblockrequest.py b/qa/rpc-tests/invalidblockrequest.py
new file mode 100755
index 0000000000..8b685ed9b2
--- /dev/null
+++ b/qa/rpc-tests/invalidblockrequest.py
@@ -0,0 +1,115 @@
+#!/usr/bin/env python2
+#
+# Distributed under the MIT/X11 software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+#
+
+from test_framework import ComparisonTestFramework
+from util import *
+from comptool import TestManager, TestInstance
+from mininode import *
+from blocktools import *
+import logging
+import copy
+import time
+
+
+'''
+In this test we connect to one node over p2p, and test block requests:
+1) Valid blocks should be requested and become chain tip.
+2) Invalid block with duplicated transaction should be re-requested.
+3) Invalid block with bad coinbase value should be rejected and not
+re-requested.
+'''
+
+# Use the ComparisonTestFramework with 1 node: only use --testbinary.
+class InvalidBlockRequestTest(ComparisonTestFramework):
+
+    ''' Can either run this test as 1 node with expected answers, or two and compare them. 
+        Change the "outcome" variable from each TestInstance object to only do the comparison. '''
+    def __init__(self):
+        self.num_nodes = 1
+
+    def run_test(self):
+        test = TestManager(self, self.options.tmpdir)
+        test.add_all_connections(self.nodes)
+        self.tip = None
+        self.block_time = None
+        NetworkThread().start() # Start up network handling in another thread
+        test.run()
+
+    def get_tests(self):
+        if self.tip is None:
+            self.tip = int ("0x" + self.nodes[0].getbestblockhash() + "L", 0)
+        self.block_time = int(time.time())+1
+
+        '''
+        Create a new block with an anyone-can-spend coinbase
+        '''
+        block = create_block(self.tip, create_coinbase(), self.block_time)
+        self.block_time += 1
+        block.solve()
+        # Save the coinbase for later
+        self.block1 = block
+        self.tip = block.sha256
+        yield TestInstance([[block, True]])
+
+        '''
+        Now we need that block to mature so we can spend the coinbase.
+        '''
+        test = TestInstance(sync_every_block=False)
+        for i in xrange(100):
+            block = create_block(self.tip, create_coinbase(), self.block_time)
+            block.solve()
+            self.tip = block.sha256
+            self.block_time += 1
+            test.blocks_and_transactions.append([block, True])
+        yield test
+
+        '''
+        Now we use merkle-root malleability to generate an invalid block with
+        same blockheader.
+        Manufacture a block with 3 transactions (coinbase, spend of prior
+        coinbase, spend of that spend).  Duplicate the 3rd transaction to 
+        leave merkle root and blockheader unchanged but invalidate the block.
+        '''
+        block2 = create_block(self.tip, create_coinbase(), self.block_time)
+        self.block_time += 1
+
+        # chr(81) is OP_TRUE
+        tx1 = create_transaction(self.block1.vtx[0], 0, chr(81), 50*100000000)
+        tx2 = create_transaction(tx1, 0, chr(81), 50*100000000)
+
+        block2.vtx.extend([tx1, tx2])
+        block2.hashMerkleRoot = block2.calc_merkle_root()
+        block2.rehash()
+        block2.solve()
+        orig_hash = block2.sha256
+        block2_orig = copy.deepcopy(block2)
+
+        # Mutate block 2
+        block2.vtx.append(tx2)
+        assert_equal(block2.hashMerkleRoot, block2.calc_merkle_root())
+        assert_equal(orig_hash, block2.rehash())
+        assert(block2_orig.vtx != block2.vtx)
+
+        self.tip = block2.sha256
+        yield TestInstance([[block2, False], [block2_orig, True]])
+
+        '''
+        Make sure that a totally screwed up block is not valid.
+        '''
+        block3 = create_block(self.tip, create_coinbase(), self.block_time)
+        self.block_time += 1
+        block3.vtx[0].vout[0].nValue = 100*100000000 # Too high!
+        block3.vtx[0].sha256=None
+        block3.vtx[0].calc_sha256()
+        block3.hashMerkleRoot = block3.calc_merkle_root()
+        block3.rehash()
+        block3.solve()
+
+        yield TestInstance([[block3, False]])
+
+
+if __name__ == '__main__':
+    InvalidBlockRequestTest().main()
diff --git a/qa/rpc-tests/test_framework.py b/qa/rpc-tests/test_framework.py
index 4c8a11b821..f61b13dfe6 100755
--- a/qa/rpc-tests/test_framework.py
+++ b/qa/rpc-tests/test_framework.py
@@ -140,3 +140,32 @@ class BitcoinTestFramework(object):
         else:
             print("Failed")
             sys.exit(1)
+
+
+# Test framework for doing p2p comparison testing, which sets up some bitcoind
+# binaries:
+# 1 binary: test binary
+# 2 binaries: 1 test binary, 1 ref binary
+# n>2 binaries: 1 test binary, n-1 ref binaries
+
+class ComparisonTestFramework(BitcoinTestFramework):
+
+    # Can override the num_nodes variable to indicate how many nodes to run.
+    def __init__(self):
+        self.num_nodes = 2
+
+    def add_options(self, parser):
+        parser.add_option("--testbinary", dest="testbinary", default="bitcoind",
+                          help="bitcoind binary to test")
+        parser.add_option("--refbinary", dest="refbinary", default="bitcoind",
+                          help="bitcoind binary to use for reference nodes (if any)")
+
+    def setup_chain(self):
+        print "Initializing test directory "+self.options.tmpdir
+        initialize_chain_clean(self.options.tmpdir, self.num_nodes)
+
+    def setup_network(self):
+        self.nodes = start_nodes(self.num_nodes, self.options.tmpdir,
+                                    extra_args=[['-debug', '-whitelist=127.0.0.1']] * self.num_nodes,
+                                    binary=[self.options.testbinary] +
+                                           [self.options.refbinary]*(self.num_nodes-1))