diff --git a/exchange/bitswap/bitswap_test.go b/exchange/bitswap/bitswap_test.go
index a68f0667f..0badc6917 100644
--- a/exchange/bitswap/bitswap_test.go
+++ b/exchange/bitswap/bitswap_test.go
@@ -2,12 +2,14 @@ package bitswap
 
 import (
 	"bytes"
+	"sync"
 	"testing"
 	"time"
 
 	context "github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/go.net/context"
 
 	ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/datastore.go"
+	"github.com/jbenet/go-ipfs/blocks"
 	bstore "github.com/jbenet/go-ipfs/blockstore"
 	exchange "github.com/jbenet/go-ipfs/exchange"
 	notifications "github.com/jbenet/go-ipfs/exchange/bitswap/notifications"
@@ -85,6 +87,64 @@ func TestGetBlockFromPeerAfterPeerAnnounces(t *testing.T) {
 	}
 }
 
+func TestSwarm(t *testing.T) {
+	net := tn.VirtualNetwork()
+	rs := tn.VirtualRoutingServer()
+	sg := NewSessionGenerator(net, rs)
+	bg := NewBlockGenerator(t)
+
+	t.Log("Create a ton of instances, and just a few blocks")
+
+	numInstances := 500
+	numBlocks := 2
+
+	instances := sg.Instances(numInstances)
+	blocks := bg.Blocks(numBlocks)
+
+	t.Log("Give the blocks to the first instance")
+
+	first := instances[0]
+	for _, b := range blocks {
+		first.blockstore.Put(*b)
+		first.exchange.HasBlock(context.Background(), *b)
+		rs.Announce(first.peer, b.Key())
+	}
+
+	t.Log("Distribute!")
+
+	var wg sync.WaitGroup
+
+	for _, inst := range instances {
+		for _, b := range blocks {
+			wg.Add(1)
+			// NB: executing getOrFail concurrently puts tremendous pressure on
+			// the goroutine scheduler
+			getOrFail(inst, b, t, &wg)
+		}
+	}
+	wg.Wait()
+
+	t.Log("Verify!")
+
+	for _, inst := range instances {
+		for _, b := range blocks {
+			if _, err := inst.blockstore.Get(b.Key()); err != nil {
+				t.Fatal(err)
+			}
+		}
+	}
+}
+
+func getOrFail(bitswap instance, b *blocks.Block, t *testing.T, wg *sync.WaitGroup) {
+	if _, err := bitswap.blockstore.Get(b.Key()); err != nil {
+		_, err := bitswap.exchange.Block(context.Background(), b.Key())
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+	wg.Done()
+}
+
 func TestSendToWantingPeer(t *testing.T) {
 	t.Log("I get a file from peer |w|. In this message, I receive |w|'s wants")
 	t.Log("Peer |w| tells me it wants file |f|, but I don't have it")
@@ -92,6 +152,31 @@ func TestSendToWantingPeer(t *testing.T) {
 	t.Log("After receiving |f| from |o|, I send it to the wanting peer |w|")
 }
 
+func NewBlockGenerator(t *testing.T) BlockGenerator {
+	return BlockGenerator{
+		T: t,
+	}
+}
+
+type BlockGenerator struct {
+	*testing.T // b/c block generation can fail
+	seq        int
+}
+
+func (bg *BlockGenerator) Next() blocks.Block {
+	bg.seq++
+	return testutil.NewBlockOrFail(bg.T, string(bg.seq))
+}
+
+func (bg *BlockGenerator) Blocks(n int) []*blocks.Block {
+	blocks := make([]*blocks.Block, 0)
+	for i := 0; i < n; i++ {
+		b := bg.Next()
+		blocks = append(blocks, &b)
+	}
+	return blocks
+}
+
 func NewSessionGenerator(
 	net tn.Network, rs tn.RoutingServer) SessionGenerator {
 	return SessionGenerator{
@@ -107,12 +192,21 @@ type SessionGenerator struct {
 	rs  tn.RoutingServer
 }
 
-func (g *SessionGenerator) Next() testnetBitSwap {
+func (g *SessionGenerator) Next() instance {
 	g.seq++
 	return session(g.net, g.rs, []byte(string(g.seq)))
 }
 
-type testnetBitSwap struct {
+func (g *SessionGenerator) Instances(n int) []instance {
+	instances := make([]instance, 0)
+	for j := 0; j < n; j++ {
+		inst := g.Next()
+		instances = append(instances, inst)
+	}
+	return instances
+}
+
+type instance struct {
 	peer       *peer.Peer
 	exchange   exchange.Interface
 	blockstore bstore.Blockstore
@@ -123,7 +217,7 @@ type testnetBitSwap struct {
 // NB: It's easy make mistakes by providing the same peer ID to two different
 // sessions. To safeguard, use the SessionGenerator to generate sessions. It's
 // just a much better idea.
-func session(net tn.Network, rs tn.RoutingServer, id peer.ID) testnetBitSwap {
+func session(net tn.Network, rs tn.RoutingServer, id peer.ID) instance {
 	p := &peer.Peer{ID: id}
 
 	adapter := net.Adapter(p)
@@ -138,7 +232,7 @@ func session(net tn.Network, rs tn.RoutingServer, id peer.ID) testnetBitSwap {
 		sender:        adapter,
 	}
 	adapter.SetDelegate(bs)
-	return testnetBitSwap{
+	return instance{
 		peer:       p,
 		exchange:   bs,
 		blockstore: blockstore,