diff --git a/chain/sync.go b/chain/sync.go
index 9864600dd..ae3f8ee80 100644
--- a/chain/sync.go
+++ b/chain/sync.go
@@ -58,7 +58,14 @@ import (
 // the theoretical max height based on systime are quickly rejected
 const MaxHeightDrift = 5
 
-var defaultMessageFetchWindowSize = 200
+var (
+	// LocalIncoming is the _local_ pubsub (unrelated to libp2p pubsub) topic
+	// where the Syncer publishes candidate chain heads to be synced.
+	LocalIncoming = "incoming"
+
+	log                           = logging.Logger("chain")
+	defaultMessageFetchWindowSize = 200
+)
 
 func init() {
 	if s := os.Getenv("LOTUS_BSYNC_MSG_WINDOW"); s != "" {
@@ -71,10 +78,6 @@ func init() {
 	}
 }
 
-var log = logging.Logger("chain")
-
-var LocalIncoming = "incoming"
-
 // Syncer is in charge of running the chain synchronization logic. As such, it
 // is tasked with these functions, amongst others:
 //
@@ -119,7 +122,7 @@ type Syncer struct {
 
 	self peer.ID
 
-	syncmgr *SyncManager
+	syncmgr SyncManager
 
 	connmgr connmgr.ConnManager
 
@@ -140,8 +143,10 @@ type Syncer struct {
 	ds dtypes.MetadataDS
 }
 
+type SyncManagerCtor func(syncFn SyncFunc) SyncManager
+
 // NewSyncer creates a new Syncer object.
-func NewSyncer(ds dtypes.MetadataDS, sm *stmgr.StateManager, exchange exchange.Client, connmgr connmgr.ConnManager, self peer.ID, beacon beacon.Schedule, verifier ffiwrapper.Verifier) (*Syncer, error) {
+func NewSyncer(ds dtypes.MetadataDS, sm *stmgr.StateManager, exchange exchange.Client, syncMgrCtor SyncManagerCtor, connmgr connmgr.ConnManager, self peer.ID, beacon beacon.Schedule, verifier ffiwrapper.Verifier) (*Syncer, error) {
 	gen, err := sm.ChainStore().GetGenesis()
 	if err != nil {
 		return nil, xerrors.Errorf("getting genesis block: %w", err)
@@ -181,7 +186,7 @@ func NewSyncer(ds dtypes.MetadataDS, sm *stmgr.StateManager, exchange exchange.C
 		log.Warn("*********************************************************************************************")
 	}
 
-	s.syncmgr = NewSyncManager(s.Sync)
+	s.syncmgr = syncMgrCtor(s.Sync)
 	return s, nil
 }
 
@@ -1665,11 +1670,7 @@ func VerifyElectionPoStVRF(ctx context.Context, worker address.Address, rand []b
 }
 
 func (syncer *Syncer) State() []SyncerState {
-	var out []SyncerState
-	for _, ss := range syncer.syncmgr.syncStates {
-		out = append(out, ss.Snapshot())
-	}
-	return out
+	return syncer.syncmgr.State()
 }
 
 // MarkBad manually adds a block to the "bad blocks" cache.
diff --git a/chain/sync_manager.go b/chain/sync_manager.go
index 8c77b47c5..811092bc7 100644
--- a/chain/sync_manager.go
+++ b/chain/sync_manager.go
@@ -20,7 +20,28 @@ const (
 
 type SyncFunc func(context.Context, *types.TipSet) error
 
-type SyncManager struct {
+// SyncManager manages the chain synchronization process, both at bootstrap time
+// and during ongoing operation.
+//
+// It receives candidate chain heads in the form of tipsets from peers,
+// and schedules them onto sync workers, deduplicating processing for
+// already-active syncs.
+type SyncManager interface {
+	// Start starts the SyncManager.
+	Start()
+
+	// Stop stops the SyncManager.
+	Stop()
+
+	// SetPeerHead informs the SyncManager that the supplied peer reported the
+	// supplied tipset.
+	SetPeerHead(ctx context.Context, p peer.ID, ts *types.TipSet)
+
+	// State retrieves the state of the sync workers.
+	State() []SyncerState
+}
+
+type syncManager struct {
 	lk        sync.Mutex
 	peerHeads map[peer.ID]*types.TipSet
 
@@ -48,6 +69,8 @@ type SyncManager struct {
 	workerChan     chan *types.TipSet
 }
 
+var _ SyncManager = (*syncManager)(nil)
+
 type syncResult struct {
 	ts      *types.TipSet
 	success bool
@@ -55,8 +78,8 @@ type syncResult struct {
 
 const syncWorkerCount = 3
 
-func NewSyncManager(sync SyncFunc) *SyncManager {
-	return &SyncManager{
+func NewSyncManager(sync SyncFunc) SyncManager {
+	return &syncManager{
 		bspThresh:       1,
 		peerHeads:       make(map[peer.ID]*types.TipSet),
 		syncTargets:     make(chan *types.TipSet),
@@ -69,18 +92,18 @@ func NewSyncManager(sync SyncFunc) *SyncManager {
 	}
 }
 
-func (sm *SyncManager) Start() {
+func (sm *syncManager) Start() {
 	go sm.syncScheduler()
 	for i := 0; i < syncWorkerCount; i++ {
 		go sm.syncWorker(i)
 	}
 }
 
-func (sm *SyncManager) Stop() {
+func (sm *syncManager) Stop() {
 	close(sm.stop)
 }
 
-func (sm *SyncManager) SetPeerHead(ctx context.Context, p peer.ID, ts *types.TipSet) {
+func (sm *syncManager) SetPeerHead(ctx context.Context, p peer.ID, ts *types.TipSet) {
 	sm.lk.Lock()
 	defer sm.lk.Unlock()
 	sm.peerHeads[p] = ts
@@ -105,6 +128,14 @@ func (sm *SyncManager) SetPeerHead(ctx context.Context, p peer.ID, ts *types.Tip
 	sm.incomingTipSets <- ts
 }
 
+func (sm *syncManager) State() []SyncerState {
+	ret := make([]SyncerState, 0, len(sm.syncStates))
+	for _, s := range sm.syncStates {
+		ret = append(ret, s.Snapshot())
+	}
+	return ret
+}
+
 type syncBucketSet struct {
 	buckets []*syncTargetBucket
 }
@@ -234,7 +265,7 @@ func (stb *syncTargetBucket) heaviestTipSet() *types.TipSet {
 	return best
 }
 
-func (sm *SyncManager) selectSyncTarget() (*types.TipSet, error) {
+func (sm *syncManager) selectSyncTarget() (*types.TipSet, error) {
 	var buckets syncBucketSet
 
 	var peerHeads []*types.TipSet
@@ -258,7 +289,7 @@ func (sm *SyncManager) selectSyncTarget() (*types.TipSet, error) {
 	return buckets.Heaviest(), nil
 }
 
-func (sm *SyncManager) syncScheduler() {
+func (sm *syncManager) syncScheduler() {
 
 	for {
 		select {
@@ -280,7 +311,7 @@ func (sm *SyncManager) syncScheduler() {
 	}
 }
 
-func (sm *SyncManager) scheduleIncoming(ts *types.TipSet) {
+func (sm *syncManager) scheduleIncoming(ts *types.TipSet) {
 	log.Debug("scheduling incoming tipset sync: ", ts.Cids())
 	if sm.getBootstrapState() == BSStateSelected {
 		sm.setBootstrapState(BSStateScheduled)
@@ -328,10 +359,11 @@ func (sm *SyncManager) scheduleIncoming(ts *types.TipSet) {
 	}
 }
 
-func (sm *SyncManager) scheduleProcessResult(res *syncResult) {
+func (sm *syncManager) scheduleProcessResult(res *syncResult) {
 	if res.success && sm.getBootstrapState() != BSStateComplete {
 		sm.setBootstrapState(BSStateComplete)
 	}
+
 	delete(sm.activeSyncs, res.ts.Key())
 	relbucket := sm.activeSyncTips.PopRelated(res.ts)
 	if relbucket != nil {
@@ -360,7 +392,7 @@ func (sm *SyncManager) scheduleProcessResult(res *syncResult) {
 	}
 }
 
-func (sm *SyncManager) scheduleWorkSent() {
+func (sm *syncManager) scheduleWorkSent() {
 	hts := sm.nextSyncTarget.heaviestTipSet()
 	sm.activeSyncs[hts.Key()] = hts
 
@@ -372,7 +404,7 @@ func (sm *SyncManager) scheduleWorkSent() {
 	}
 }
 
-func (sm *SyncManager) syncWorker(id int) {
+func (sm *syncManager) syncWorker(id int) {
 	ss := &SyncerState{}
 	sm.syncStates[id] = ss
 	for {
@@ -397,7 +429,7 @@ func (sm *SyncManager) syncWorker(id int) {
 	}
 }
 
-func (sm *SyncManager) syncedPeerCount() int {
+func (sm *syncManager) syncedPeerCount() int {
 	var count int
 	for _, ts := range sm.peerHeads {
 		if ts.Height() > 0 {
@@ -407,19 +439,19 @@ func (sm *SyncManager) syncedPeerCount() int {
 	return count
 }
 
-func (sm *SyncManager) getBootstrapState() int {
+func (sm *syncManager) getBootstrapState() int {
 	sm.bssLk.Lock()
 	defer sm.bssLk.Unlock()
 	return sm.bootstrapState
 }
 
-func (sm *SyncManager) setBootstrapState(v int) {
+func (sm *syncManager) setBootstrapState(v int) {
 	sm.bssLk.Lock()
 	defer sm.bssLk.Unlock()
 	sm.bootstrapState = v
 }
 
-func (sm *SyncManager) IsBootstrapped() bool {
+func (sm *syncManager) IsBootstrapped() bool {
 	sm.bssLk.Lock()
 	defer sm.bssLk.Unlock()
 	return sm.bootstrapState == BSStateComplete
diff --git a/chain/sync_manager_test.go b/chain/sync_manager_test.go
index ca2ced856..269b3a62e 100644
--- a/chain/sync_manager_test.go
+++ b/chain/sync_manager_test.go
@@ -17,7 +17,7 @@ type syncOp struct {
 	done func()
 }
 
-func runSyncMgrTest(t *testing.T, tname string, thresh int, tf func(*testing.T, *SyncManager, chan *syncOp)) {
+func runSyncMgrTest(t *testing.T, tname string, thresh int, tf func(*testing.T, *syncManager, chan *syncOp)) {
 	syncTargets := make(chan *syncOp)
 	sm := NewSyncManager(func(ctx context.Context, ts *types.TipSet) error {
 		ch := make(chan struct{})
@@ -27,7 +27,7 @@ func runSyncMgrTest(t *testing.T, tname string, thresh int, tf func(*testing.T,
 		}
 		<-ch
 		return nil
-	})
+	}).(*syncManager)
 	sm.bspThresh = thresh
 
 	sm.Start()
@@ -77,12 +77,12 @@ func TestSyncManager(t *testing.T) {
 	c3 := mock.TipSet(mock.MkBlock(b, 3, 5))
 	d := mock.TipSet(mock.MkBlock(c1, 4, 5))
 
-	runSyncMgrTest(t, "testBootstrap", 1, func(t *testing.T, sm *SyncManager, stc chan *syncOp) {
+	runSyncMgrTest(t, "testBootstrap", 1, func(t *testing.T, sm *syncManager, stc chan *syncOp) {
 		sm.SetPeerHead(ctx, "peer1", c1)
 		assertGetSyncOp(t, stc, c1)
 	})
 
-	runSyncMgrTest(t, "testBootstrap", 2, func(t *testing.T, sm *SyncManager, stc chan *syncOp) {
+	runSyncMgrTest(t, "testBootstrap", 2, func(t *testing.T, sm *syncManager, stc chan *syncOp) {
 		sm.SetPeerHead(ctx, "peer1", c1)
 		assertNoOp(t, stc)
 
@@ -90,7 +90,7 @@ func TestSyncManager(t *testing.T) {
 		assertGetSyncOp(t, stc, c1)
 	})
 
-	runSyncMgrTest(t, "testSyncAfterBootstrap", 1, func(t *testing.T, sm *SyncManager, stc chan *syncOp) {
+	runSyncMgrTest(t, "testSyncAfterBootstrap", 1, func(t *testing.T, sm *syncManager, stc chan *syncOp) {
 		sm.SetPeerHead(ctx, "peer1", b)
 		assertGetSyncOp(t, stc, b)
 
@@ -101,7 +101,7 @@ func TestSyncManager(t *testing.T) {
 		assertGetSyncOp(t, stc, c2)
 	})
 
-	runSyncMgrTest(t, "testCoalescing", 1, func(t *testing.T, sm *SyncManager, stc chan *syncOp) {
+	runSyncMgrTest(t, "testCoalescing", 1, func(t *testing.T, sm *syncManager, stc chan *syncOp) {
 		sm.SetPeerHead(ctx, "peer1", a)
 		assertGetSyncOp(t, stc, a)
 
@@ -122,7 +122,7 @@ func TestSyncManager(t *testing.T) {
 		assertGetSyncOp(t, stc, d)
 	})
 
-	runSyncMgrTest(t, "testSyncIncomingTipset", 1, func(t *testing.T, sm *SyncManager, stc chan *syncOp) {
+	runSyncMgrTest(t, "testSyncIncomingTipset", 1, func(t *testing.T, sm *syncManager, stc chan *syncOp) {
 		sm.SetPeerHead(ctx, "peer1", a)
 		assertGetSyncOp(t, stc, a)
 
diff --git a/node/builder.go b/node/builder.go
index 6c01258a6..bf11145df 100644
--- a/node/builder.go
+++ b/node/builder.go
@@ -242,6 +242,9 @@ func Online() Option {
 			Override(new(dtypes.ChainBlockService), modules.ChainBlockService),
 
 			// Filecoin services
+			// We don't want the SyncManagerCtor to be used as an fx constructor, but rather as a value.
+			// It will be called implicitly by the Syncer constructor.
+			Override(new(chain.SyncManagerCtor), func() chain.SyncManagerCtor { return chain.NewSyncManager }),
 			Override(new(*chain.Syncer), modules.NewSyncer),
 			Override(new(exchange.Client), exchange.NewClient),
 			Override(new(*messagepool.MessagePool), modules.MessagePool),
diff --git a/node/modules/chain.go b/node/modules/chain.go
index 7b7e03e44..5eda51078 100644
--- a/node/modules/chain.go
+++ b/node/modules/chain.go
@@ -163,8 +163,31 @@ func NetworkName(mctx helpers.MetricsCtx, lc fx.Lifecycle, cs *store.ChainStore,
 	return netName, err
 }
 
-func NewSyncer(lc fx.Lifecycle, ds dtypes.MetadataDS, sm *stmgr.StateManager, exchange exchange.Client, h host.Host, beacon beacon.Schedule, verifier ffiwrapper.Verifier) (*chain.Syncer, error) {
-	syncer, err := chain.NewSyncer(ds, sm, exchange, h.ConnManager(), h.ID(), beacon, verifier)
+type SyncerParams struct {
+	fx.In
+
+	Lifecycle    fx.Lifecycle
+	MetadataDS   dtypes.MetadataDS
+	StateManager *stmgr.StateManager
+	ChainXchg    exchange.Client
+	SyncMgrCtor  chain.SyncManagerCtor
+	Host         host.Host
+	Beacon       beacon.Schedule
+	Verifier     ffiwrapper.Verifier
+}
+
+func NewSyncer(params SyncerParams) (*chain.Syncer, error) {
+	var (
+		lc     = params.Lifecycle
+		ds     = params.MetadataDS
+		sm     = params.StateManager
+		ex     = params.ChainXchg
+		smCtor = params.SyncMgrCtor
+		h      = params.Host
+		b      = params.Beacon
+		v      = params.Verifier
+	)
+	syncer, err := chain.NewSyncer(ds, sm, ex, smCtor, h.ConnManager(), h.ID(), b, v)
 	if err != nil {
 		return nil, err
 	}