diff --git a/zipline/finance/sources.py b/zipline/finance/sources.py
index 9cde473c..b9f818ea 100644
--- a/zipline/finance/sources.py
+++ b/zipline/finance/sources.py
@@ -83,7 +83,7 @@ class RandomEquityTrades(TradeDataSource):
 
 class SpecificEquityTrades(TradeDataSource):
     """
-    Generates a random stream of trades for testing.
+    Generates a non-random stream of trades for testing.
     """
 
     def init(self, event_list):
diff --git a/zipline/gens/composites.py b/zipline/gens/composites.py
index 1b710212..5ee45de6 100644
--- a/zipline/gens/composites.py
+++ b/zipline/gens/composites.py
@@ -1,17 +1,80 @@
+import datetime
+from itertools import tee
 
+from zipline.gens.tradegens import SpecificEquityTrades
+from zipline.gens.utils import roundrobin, hash_args
 from zipline.gens.feed import FeedGen
-from zipline.gens.tradegen import SpecificEquityTrades
-from zipline.gens.transform 
+from zipline.gens.merge import MergeGen
+from zipline.gens.transform import StatefulTransformGen
 
-
-
-
-def PreTransformLayer(sources):
-    """A generator that takes a list of sources and runs their output
-    through a FeedGen."""
-    not_finished = len_
-
-    while not_finished:
-        
-        
+def PreTransformLayer(sources, source_args, source_kwargs):
+    """
+    Takes a list of generator functions, a list of tuples of positional arguments,
+    and a list of dictionaries of keyword arguments.  Packages up all arguments
+    and passes them into a FeedGen.
+    """
+    assert len(sources) == len(source_args) == len(source_kwargs)
+    # Package up sources and arguments.
+    arg_bundles = zip(sources, source_args, source_kwargs)
+    
+    # Calculate namestring hashes to pass to FeedGen.
+    namestrings = [source.__name__ + hash_args(*args, **kwargs)
+                   for source, args, kwargs in arg_bundles]
+    # Pass each source its arguments.
+    initialized = tuple(source(*args, **kwargs)
+                        for source, args, kwargs in arg_bundles)
+    
+    stream_in = roundrobin(*initialized)
+    return FeedGen(stream_in, namestrings)
+
+
+def TransformLayer(feed_stream, tnfms, tnfm_args, tnfm_kwargs):
+    """ 
+    A generator that takes the expected output of a FeedGen, pipes it
+    through a given set of transforms, and runs the results throught a
+    MergeGen to output a unified stream. tnfms should be a list of
+    pointers to generator functions. tnfm_args should be a list of
+    tuples, representing the arguments to be passed to each transform.
+    tnfm_kwargs should be a list of dictionaries representing keyword
+    arguments to each transform.
+    """
+
+    # We should have as many sets of args as we have transforms.
+    assert len(tnfms) == len(tnfm_args) == len(tnfm_kwargs)
+
+    # Create a copy of the stream for each transform.
+    split = tee(feed_stream, len(tnfms))
+    
+    # Package each stream copy with a transform and set of args.  Use a list
+    # so that we can re-use this for calculating hashes.
+    bundles = zip(split, tnfms, tnfm_args, tnfm_kwargs)
+ 
+    tnfm_gens = [StatefulTransformGen(stream, tnfm, *args, **kwargs)
+                 for stream, tnfm, args, kwargs in bundles]
+    
+    # Generate expected hashes for each transform
+    hashes = [tnfm.__name__ + hash_args(*args, **kwargs) 
+              for _, tnfm, args, kwargs in bundles]
+              
+    # Roundrobin the outputs of our transforms to create a single flat stream.
+    to_merge = roundrobin(*tnfm_gens)
+    
+    # Pipe the stream into MergeGen.
+    merged = MergeGen(to_merge, hashes)
+    return merged
+
+if __name__ == "__main__":
+    from zipline.gens.transform import MovingAverage, Passthrough
+    
+    import nose.tools; nose.tools.set_trace()
+    source = SpecificEquityTrades
+    feed_out = PreTransformLayer((source,), ((),), ({},))
+
+    transforms = [MovingAverage, Passthrough]
+    args = [(datetime.timedelta(days = 1), ['price']), ()]
+    kwargs = [{}, {}]
+    
+    tlayer = TransformLayer(feed_out, transforms, args, kwargs)
+    
+    
     
diff --git a/zipline/gens/feed.py b/zipline/gens/feed.py
index e7498d5c..f029d0ee 100644
--- a/zipline/gens/feed.py
+++ b/zipline/gens/feed.py
@@ -13,7 +13,8 @@ from collections import deque, defaultdict
 
 from zipline import ndict
 from zipline.gens.utils import hash_args, assert_datasource_protocol, \
-    assert_trade_protocol, assert_datasource_unframe_protocol
+    assert_trade_protocol, assert_datasource_unframe_protocol, \
+    assert_feed_protocol
 
 import zipline.protocol as zp
 
@@ -38,7 +39,7 @@ def FeedGen(stream_in, source_ids):
         # Incoming messages should be the output of DATASOURCE_UNFRAME.
         assert_datasource_unframe_protocol(message), \
             "Bad message in FeedGen: %s" % message
-
+        
         # Only allow messages from sources we expect.
         assert message.source_id in sources, "Unexpected source: %s" % message
 
@@ -49,9 +50,9 @@ def FeedGen(stream_in, source_ids):
 
         while full(sources) and not done(sources):
             message = pop_oldest(sources)
-            assert feed_protocol(message)
+            assert_feed_protocol(message)
             yield message
-
+    
     # We should have only a done message left in each queue.    
     for queue in sources.itervalues():
         assert len(queue) == 1, "Bad queue in FeedGen on exit: %s" % queue
@@ -60,8 +61,9 @@ def FeedGen(stream_in, source_ids):
 
 def full(sources):
     """
-    Feed is full when every internal queue has at least one message. Note that
-    this include DONE messages, so done(sources) is True only if full(sources).
+    Feed is full when every internal queue has at least one
+    message. Note that this include DONE messages, so done(sources) is
+    True only if full(sources).
     """
     assert isinstance(sources, dict)
     return all( (queue_is_full(source) for source in sources.itervalues()) )
diff --git a/zipline/gens/merge.py b/zipline/gens/merge.py
index 7c0a195c..52adcb84 100644
--- a/zipline/gens/merge.py
+++ b/zipline/gens/merge.py
@@ -13,7 +13,7 @@ from collections import deque, defaultdict
 
 from zipline import ndict
 from zipline.gens.utils import hash_args, assert_datasource_protocol, \
-    assert_trade_protocol, assert_datasource_unframe_protocol
+    assert_trade_protocol, assert_datasource_unframe_protocol, assert_merge_protocol
 
 import zipline.protocol as zp
 
@@ -25,44 +25,46 @@ def MergeGen(stream_in, tnfm_ids):
     and merge them together into an event.  We raise an error if we 
     do not receive the same number of events from all sources.
     """
-    
-    assert isinstance(source_ids, list)
 
+    assert isinstance(tnfm_ids, list)
+    
     # Set up an internal queue for each expected source.
-    sources = {}
-    for id in source_ids:
-        assert isinstance(id, basestring), "Bad source_id %s" % source_id
-        sources[id] = deque()
+    tnfms = {}
+    for id in tnfm_ids:
+        assert isinstance(id, basestring), "Bad source_id %s" % id
+        tnfms[id] = deque()
 
     # Process incoming streams.
     for message in stream_in:
-        assert isinstance(message, ndict), \
+        assert isinstance(message, tuple), \
             "Bad message in MergeGen: %s" %message
-        assert message.tnfm_id in tnfm_ids, \
-            "Message from unexpected tnfm: %s, %s" % (message, tnfm_ids)
+        assert len(message) == 2
+        id, value = message
+        assert id in tnfm_ids, \
+            "Message from unexpected tnfm: %s, %s" % (id, tnfm_ids)
+        assert isinstance(value, ndict), "Bad message in MergeGen: %s" %message
 
-        assert message.has_key('value')
-
-        source[message.tnfm_id].append(message)
+        tnfms[id].append(value)
 
         # Only pop messages when we have a pending message from
         # all datasources. Stop if all sources have signalled done.
 
-        while full(sources) and not done(sources):
-            message = merge_one(sources)
-            assert merge_protocol(message)
+        while full(tnfms) and not done(tnfms):
+            message = merge_one(tnfms)
+            assert_merge_protocol(tnfm_ids, message)
             yield message
 
     # We should have only a done message left in each queue.    
-    for queue in sources.itervalues():
+    for queue in tnfms.itervalues():
         assert len(queue) == 1, "Bad queue in MergeGen on exit: %s" % queue
         assert queue[0].dt == "DONE", \
             "Bad last message in MergeGen on exit: %s" % queue
 
 def merge_one(sources):
     output = ndict()
-    for queue in sources.itervalues():
-        output.merge(queue.popleft())
+    for key, queue in sources.iteritems():
+        new_xform = ndict({key: queue.popleft()})
+        output.merge(new_xform)
     return output
 
 
diff --git a/zipline/gens/test_feed.py b/zipline/gens/test_feed.py
index 5e632f9d..b5007b91 100644
--- a/zipline/gens/test_feed.py
+++ b/zipline/gens/test_feed.py
@@ -13,8 +13,10 @@ from collections import deque
 from zipline import ndict
 from zipline.gens.feed import FeedGen, full, done, queue_is_full,queue_is_done,\
     pop_oldest
-from zipline.gens.utils import stringify_args, assert_datasource_protocol,\
-    assert_trade_protocol, date_gen, alternate
+from zipline.gens.utils import hash_args, assert_datasource_protocol,\
+    assert_trade_protocol, alternate
+from zipline.gens.tradegens import date_gen, SpecificEquityTrades
+from zipline.gens.composites import PreTransformLayer
 
 import zipline.protocol as zp
 
@@ -98,12 +100,11 @@ class FeedGenTestCase(TestCase):
         l = list(feed_gen)
         assert l == expected
         
-
     def test_single_source(self):
         source_ids = ['a']
         # 100 events, increasing by a minute at a time.
         type = zp.DATASOURCE_TYPE.TRADE
-        dates = list(date_gen(n = 1))
+        dates = list(date_gen(count = 100))
         dates.append("DONE")
         
         # [('a', date1, type), ('a', date2, type), ... ('a', "DONE", type)]
@@ -125,7 +126,7 @@ class FeedGenTestCase(TestCase):
 
         # Set up source 'a'. Outputs 20 events with 2 minute deltas.
         delta_a = timedelta(minutes = 2)
-        dates_a = list(date_gen(delta = delta_a, n = 20))
+        dates_a = list(date_gen(delta = delta_a, count = 20))
         dates_a.append("DONE")
 
         events_a_args = zip(cycle(['a']), iter(dates_a), cycle([type]))
@@ -133,7 +134,7 @@ class FeedGenTestCase(TestCase):
         
         # Set up source 'b'. Outputs 10 events with 1 minute deltas.
         delta_b = timedelta(minutes = 1)
-        dates_b = list(date_gen(delta = delta_b, n = 10))
+        dates_b = list(date_gen(delta = delta_b, count = 10))
         dates_b.append("DONE")
 
         events_b_args = zip(cycle(['b']), iter(dates_b), cycle([type]))
@@ -152,13 +153,65 @@ class FeedGenTestCase(TestCase):
 
         sequential = chain(iter(events_a), iter(events_b))
         self.run_FeedGen(sequential, expected, source_ids)
+
+    def test_full_feed_layer(self):
+        
+        filter = [1,2]
+        #Set up source a. One hour between events.
+        args_a = tuple()
+        kwargs_a = {'sids'   : [1,2,3,4],
+                    'start'  : datetime(2012,6,6,0),
+                    'delta'  : timedelta(hours = 1),
+                    'filter' : filter
+        }
+        #Set up source b. One day between events.       
+        args_b = tuple()
+        kwargs_b = {'sids'   : [1,2,3,4],
+                    'start'  : datetime(2012,6,6,0),
+                    'delta'  : timedelta(days = 1),
+                    'filter' : filter
+        }
+        #Set up source c. One minute between events.
+        args_c = tuple()
+        kwargs_c = {'sids'   : [1,2,3,4],
+                    'start'  : datetime(2012,6,6,0),
+                    'delta'  : timedelta(minutes = 1),
+                    'filter' : filter
+        }
+        # Set up source d. This should produce no events because the
+        # internal sids don't match the filter.
+        args_d = tuple()
+        kwargs_d = {'sids'   : [3,4],
+                    'start'  : datetime(2012,6,6,0),
+                    'delta'  : timedelta(minutes = 1),
+                    'filter' : filter
+        }
+        
+        sources = (SpecificEquityTrades,) * 4
+        source_args = (args_a, args_b, args_c, args_d)
+        source_kwargs = (kwargs_a, kwargs_b, kwargs_c, kwargs_d)
+        
+        # Generate our expected source_ids.
+        zip_args = zip(source_args, source_kwargs)
+        expected_ids = ["SpecificEquityTrades" + hash_args(*args, **kwargs)
+                        for args, kwargs in zip_args]
+        
+        # Pipe our sources into feed.
+        feed_out = PreTransformLayer(sources, source_args, source_kwargs)
+        
+        # Read all the values from feed and assert that they arrive in
+        # the correct sorting with the expected hash values.
+        to_list = list(feed_out)
+        copy = to_list[:]
+        for e in to_list:
+            # All events should match one of our expected source_ids.
+            assert e.source_id in expected_ids
+            # But none of them should match source_d.
+            assert e.source_id != hash_args(*args_d, **kwargs_d)
+
+        expected = sorted(copy, compare_by_dt_source_id)
+        assert to_list == expected
     
-        def test_with_specific_equity(self):
-            
-            
-        
-        
-        
 def mock_data_unframe(source_id, dt, type):
     event = ndict()
     event.source_id = source_id
@@ -182,7 +235,3 @@ def compare_by_dt_source_id(x,y):
     
     else:
         return 0
-        
-        
-        
-        
diff --git a/zipline/gens/test_mongods.py b/zipline/gens/test_mongods.py
index ea19d90e..d9b8dbe5 100644
--- a/zipline/gens/test_mongods.py
+++ b/zipline/gens/test_mongods.py
@@ -10,7 +10,7 @@ from itertools import izip, izip_longest
 from datetime import datetime, timedelta
 
 from zipline.gens.mongods import create_pymongo_iterator, MongoTradeHistoryGen
-from zipline.gens.utils import stringify_args, assert_datasource_protocol,\
+from zipline.gens.utils import hash_args, assert_datasource_protocol,\
     assert_trade_protocol, mock_raw_event
 
 import zipline.protocol as zp
@@ -107,7 +107,7 @@ class TestMongoDataGenerator(TestCase):
                 for field in iter(['sid', 'dt', 'price', 'volume']):
                     assert db[field] == expected[field]
                 
-                # Expected output of stringify_args:
+                # Expected output of hash_args:
                 assert db['source_id'] == \
                     'MongoTradeHistoryGen983a27fd0710414239a5cde71ef5a8fc'
                 
diff --git a/zipline/gens/tradegens.py b/zipline/gens/tradegens.py
index 24ece45b..fb0b3f48 100644
--- a/zipline/gens/tradegens.py
+++ b/zipline/gens/tradegens.py
@@ -1,44 +1,126 @@
 import random
-from itertools import chain, repeat, cycle, ifilter
+from itertools import chain, repeat, cycle, ifilter, izip
 from datetime import datetime, timedelta
 
-from zipline.utils.factory import create_trade, create_trade
-from zipline.gens.utils import date_gen
+from zipline.utils.factory import create_trade
+from zipline.gens.utils import hash_args, mock_done
 
-def mock_prices(n, rand = False):
-    """Utility to generate a set of prices. By default
-    cycles through values from 0.0 to 10.0 n times.  Optional
-    flag to give random values between 0.0 and 10.0"""
+def date_gen(start = datetime(2012, 6, 6, 0),
+             delta = timedelta(minutes = 1), 
+             count = 100):
+    """
+    Utility to generate a stream of dates.
+    """
+    return (start + (i * delta) for i in xrange(count))
+
+def mock_prices(count, rand = False):
+    """
+    Utility to generate a stream of mock prices. By default
+    cycles through values from 0.0 to 10.0, n times.  Optional
+    flag to give random values between 0.0 and 10.0
+    """
 
     if rand:
-        return (random.uniform(0.0, 10.0) for i in xrange(n))
+        return (random.uniform(0.0, 10.0) for i in xrange(count))
     else:
-        return (float(i % 11) for i in xrange(1,n+1))
+        return (float(i % 11) for i in xrange(1,count+1))
 
-def mock_volumes(n, rand = False):
-    """Does the same as mock_prices.  Different function name
-    for readability."""
-    return mock_prices(n, rand)
-
-def SpecificEquityTrades(n = 500, sids = [1, 2], event_list = None, filter = None):
-    """Returns the first n events of event_list if specified. 
-    Otherwise generates a sensible stream of events."""
+def mock_volumes(count, rand = False):
+    """
+    Utility to generate a set of volumes. By default cycles
+    through values from 100 to 1000, incrementing by 50.  Optional
+    flag to give random values between 100 and 1000. 
+    """
+    if rand:
+        return (random.randrange(100, 1000) for i in xrange(count))
+    else:
+        return ((i * 50)%900 + 100 for i in xrange(count))
     
+def fuzzy_dates(count = 500):
+    """
+    Add +-10 seconds to each event from a date_gen.  Note that this
+    still guarantees sorting, since the default on date_gen is minute
+    separation of events.
+    """
+    for date in date_gen(count = count):
+        yield date + timedelta(seconds = random.randint(-10, 10)) 
+
+def SpecificEquityTrades(*args, **config):
+    """
+    Yields all events in event_list that match the given sid_filter.
+    If no event_list is specified, generates an internal stream of events
+    to filter.  Returns all events if filter is None.
+    """
+    # We shouldn't get any positional arguments.
+    assert args == ()
+
+    # Unpack config dictionary with default values.
+    count = config.get('count', 500)
+    sids = config.get('sids', [1, 2])
+    start = config.get('start', datetime(2012, 6, 6, 0))
+    delta = config.get('delta', timedelta(minutes = 1))
+
+    # Default to None for event_list and filter.
+    event_list = config.get('event_list') 
+    filter = config.get('filter')
+
+    arg_string = hash_args(*args, **config)
+    namestring = "SpecificEquityTrades" + arg_string
+    # If we have an event_list, ignore the other arguments and use the list.
+    # TODO: still append our namestring?
     if event_list:
         unfiltered = (event for event in event_list)
-    
+
+    # Set up iterators for each expected field.
     else:
-        dates = date_gen(n = n)
-        prices = mock_prices(n)
-        volumes = mock_volumes(n)
-        sids = cycle(iter(sids))
-        
+        dates = date_gen(count = count, start = start, delta = delta)
+        prices = mock_prices(count)
+        volumes = mock_volumes(count)
+        sids = cycle(sids)
+
+        # Combine the iterators into a single iterator of arguments
         arg_gen = izip(sids, prices, volumes, dates)
-        
-        unfiltered = (create_trade(*args) for args in arg_gen)
+
+        # Convert argument packages into events.
+        unfiltered = (create_trade(*args, source_id = namestring)
+                      for args in arg_gen)
+
+    # If we specified a sid filter, filter out elements that don't match the filter.
     if filter:
-        filtered = ifilter(lambda event: event.sid in filter)
+        filtered = ifilter(lambda event: event.sid in filter, unfiltered)
+
+    # Otherwise just use all events.
     else:
         filtered = unfiltered
 
+    # Add a done message to the end of the stream. For a live
+    # datasource this would be handled by the containing Component.
+    out = chain(filtered, [mock_done(namestring)])
+    return out
+
+def RandomEquityTrades(*args, **config):
+    # We shouldn't get any positional args.
+    assert args == ()
+    
+    count = config.get('count', 500)
+    sids = config.get('sids', [1,2])
+    filter = config.get('filter')
+
+    dates = fuzzy_dates(count)
+    prices = mock_prices(count, rand = True)
+    volumes = mock_volumes(count, rand = True)
+    sids = cycle(sids)
+
+    arg_gen = izip(sids, prices, volumes, dates)
+    
+    unfiltered = (create_trade(*args) for args in arg_gen)
+    
+    if filter:
+        filtered = ifilter(lambda event: event.sid in filter, unfiltered)
+    else:
+        filtered = unfiltered
     return filtered
+
+# if __name__ == "__main__":
+#     import nose.tools; nose.tools.set_trace()
+#     trades = SpecificEquityTrades(filter = [1])
diff --git a/zipline/gens/transform.py b/zipline/gens/transform.py
index bdd85ee9..137b9d69 100644
--- a/zipline/gens/transform.py
+++ b/zipline/gens/transform.py
@@ -14,26 +14,24 @@ from numbers import Number
 from itertools import izip
 
 from zipline import ndict
-from zipline.gens.utils import hash_args, date_gen
-from zipline.gens.utils import  assert_feed_unframe_protocol, assert_transform_protocol
+from zipline.gens.tradegens import date_gen
+from zipline.gens.utils import assert_feed_unframe_protocol, \
+    assert_transform_protocol, hash_args
 
 import zipline.protocol as zp
 
-def PassthroughTransformGen(stream_in):
-    """Trivial transform for event forwarding."""
+class Passthrough(object):
+    """
+    Trivial function for forwarding events.
+    """
+    def __init__(self):
+        pass
 
-    # hash_args with no arguments is the same as:
-    # hasher = hashlib.md5() 
-    # hasher.update(":"); 
-    # hashlib.md5.digest().
-
-    namestring = "Passthrough" + hash_args()
-
-    for message in stream_in:
-        assert_feed_unframe_protocol(message)
-        out_value = message
-        assert_transform_protocol(out_value)
-        yield (namestring, out_value)
+    def update(self, event):        
+        assert isinstance(event, ndict),"Bad event in Passthrough: %s" % event
+        assert event.has_key('sid'), "No sid in Passthrough: %s" % event
+        assert event.has_key('dt'), "No dt in Passthorughz: %s" % event
+        return event
 
 def FunctionalTransformGen(stream_in, fun, *args, **kwargs):
     """
@@ -43,6 +41,10 @@ def FunctionalTransformGen(stream_in, fun, *args, **kwargs):
     """
     
     # TODO: Distinguish between functions and classes in hash_args.
+    # As implemented we will get assertion errors if a function and
+    # stateful class have the same name, which may or may not be
+    # what we want.
+
     namestring = fun.__name__ + hash_args(*args, **kwargs)
     
     for message in stream_in:
@@ -70,13 +72,6 @@ def StatefulTransformGen(stream_in, tnfm_class, *args, **kwargs):
         assert_transform_protocol(out_value)
         yield (namestring, out_value)
 
-def MovingAverageTransformGen(stream_in, days, fields):
-    """
-    Generator that uses the MovingAverage state class to calculate
-    a moving average for all stocks over a specified number of days.
-    """
-    return StatefulTransformGen(stream_in, MovingAverage, timedelta(days=days), fields)
-
 class MovingAverage(object):
     """
     Class that maintains a dictionary from sids to EventWindows
@@ -91,7 +86,7 @@ class MovingAverage(object):
         # No way to pass arguments to the defaultdict factory, so we
         # need to define a method to generate the correct EventWindows.
         self.sid_windows = defaultdict(self.create_window)
-
+        
     def create_window(self):
         """Factory method for self.sid_windows."""
         return EventWindow(self.delta, self.fields)
@@ -104,13 +99,18 @@ class MovingAverage(object):
         
         assert isinstance(event, ndict),"Bad event in MovingAverage: %s" % event
         assert event.has_key('sid'), "No sid in MovingAverage: %s" % event
+        assert event.has_key('dt'), "No dt in MovingAverage: %s" % event
         
+        output = ndict({'sid': event.sid, 'dt': event.dt})
         # This will create a new EventWindow if this is the first
         # message for this sid.
         window = self.sid_windows[event.sid]
         window.update(event)
+        averages =  window.get_averages()
         
-        return window.get_averages()
+        # Return the calculated averages along with
+        output.merge(averages)
+        return output
     
 class EventWindow(object):
     """
@@ -144,7 +144,7 @@ class EventWindow(object):
         #           newest               oldest
         #             |                    |
         #             V                    V
-        
+                
         while (self.ticks[-1].dt - self.ticks[0].dt) >= self.delta:
             # popleft removes and returns ticks[0]
             popped = self.ticks.popleft()
@@ -168,6 +168,7 @@ class EventWindow(object):
         Return an ndict of all our tracked averages.
         """
         out = ndict()
+        # out.ticks = len(self.ticks)
         for field in self.fields:
             out[field] = self.average(field)
         return out
@@ -186,26 +187,26 @@ class EventWindow(object):
             assert isinstance(event[field], Number), \
                 "Got %s for %s in EventWindow" % (event[field], field)
 
-if __name__ == "__main__":
+# if __name__ == "__main__":
 
-    def make_event(**kwargs):
-        e = ndict()
-        for key, value in kwargs.iteritems():
-            e[key] = value
-        return e
+#     def make_event(**kwargs):
+#         e = ndict()
+#         for key, value in kwargs.iteritems():
+#             e[key] = value
+#         return e
     
-    dates = date_gen(delta = timedelta(hours = 12))
-    events = ( 
-        make_event(
-            sid = 'foo', price = random.random(), 
-            dt = date, 
-            type = zp.DATASOURCE_TYPE.TRADE, 
-            source_id = 'ds',
-            vol = i
-        )
-        for date, i in izip(dates, xrange(100))
-    )
+#     dates = date_gen(delta = timedelta(hours = 12))
+#     events = ( 
+#         make_event(
+#             sid = 'foo', price = random.random(), 
+#             dt = date, 
+#             type = zp.DATASOURCE_TYPE.TRADE, 
+#             source_id = 'ds',
+#             vol = i
+#         )
+#         for date, i in izip(dates, xrange(100))
+#     )
 
-    gen = MovingAverageTransformGen(events, 1, ['price', 'vol'])
+#     gen = MovingAverageTransformGen(events, 1, ['price', 'vol'])
     
 
diff --git a/zipline/gens/utils.py b/zipline/gens/utils.py
index efe81a14..c10cffdf 100644
--- a/zipline/gens/utils.py
+++ b/zipline/gens/utils.py
@@ -16,16 +16,28 @@ def mock_raw_event(sid, dt):
     }
     return event
 
-def date_gen(start = datetime(2012, 6, 6, 0), delta = timedelta(minutes = 1), n = 100):
-    return (start + i * delta for i in xrange(n))
-
+def mock_done(source_id):
+    return ndict({'dt': "DONE", "source_id" : source_id, 'type' : 0})
+              
 def alternate(g1, g2):
+    """Specialized version of roundrobin for just 2 generators."""
     for e1, e2 in izip_longest(g1, g2):
         if e1 != None:
             yield e1
         if e2 != None:
             yield e2
 
+def roundrobin(*args):
+    """
+    Takes N generators, pulling one element off each until all inputs
+    are empty.  
+    """
+    for elem_tuple in izip_longest(*args):
+        for value in elem_tuple:
+            if value != None:
+                yield value
+
+
 def hash_args(*args, **kwargs):
     """Define a unique string for any set of representable args."""
     arg_string = '_'.join([str(arg) for arg in args])
@@ -73,14 +85,19 @@ def assert_feed_protocol(event):
     assert event.type in DATASOURCE_TYPE
     assert event.has_key('dt')
     
-    
 def assert_feed_unframe_protocol(event):
     """Same as above."""
     assert isinstance(event, ndict)
+    assert isinstance(event.source_id, basestring)
     assert event.type in DATASOURCE_TYPE
     assert event.has_key('dt')
 
-
 def assert_transform_protocol(event):
-    pass
+    """Transforms should return an ndict to be merged by MergeGen."""
+    assert isinstance(event, ndict)
+
+def assert_merge_protocol(tnfm_ids, message):
+    """Merge should output an ndict with a field for each id in its transform set."""
+    assert isinstance(message, ndict)
+    assert set(tnfm_ids) == set(message.keys())
 
diff --git a/zipline/gens/zmq_gens.py b/zipline/gens/zmq_gens.py
new file mode 100644
index 00000000..524852a7
--- /dev/null
+++ b/zipline/gens/zmq_gens.py
@@ -0,0 +1,16 @@
+import zmq
+
+import zipline.protocol as zp
+
+def gen_from_zmq(poller, unframe):
+    """
+    A generator that takes an initialized zmq poller and yields
+    messages from the poller until it gets a zp.CONTROL_PROTOCOL.DONE.
+    """
+    while True:
+        message = poller.recv()
+        if message = zp.CONTROL_PROTOCOL.DONE:
+            yield "DONE"
+            break
+        else:
+            yield unframe(message)
diff --git a/zipline/utils/factory.py b/zipline/utils/factory.py
index 23c2eb3e..db440891 100644
--- a/zipline/utils/factory.py
+++ b/zipline/utils/factory.py
@@ -69,9 +69,9 @@ def create_trading_environment(year=2006):
 
     return trading_environment
 
-def create_trade(sid, price, amount, datetime):
+def create_trade(sid, price, amount, datetime, source_id = "test_factory"):
     row = zp.ndict({
-        'source_id' : "test_factory",
+        'source_id' : source_id,
         'type'      : zp.DATASOURCE_TYPE.TRADE,
         'sid'       : sid,
         'dt'        : datetime,