core: support inserting pure header chains

5 files changed, 645 insertions, 321 deletions

diff --git a/core/block_processor.go b/core/block_processor.go
index a07d79bcf..5dadd2a27 100644
--- a/core/block_processor.go
+++ b/core/block_processor.go
@@ -369,13 +369,26 @@ func (sm *BlockProcessor) GetLogs(block *types.Block) (logs vm.Logs, err error)
 	return logs, nil
 }
 
+// ValidateHeader verifies the validity of a header, relying on the database and
+// POW behind the block processor.
+func (sm *BlockProcessor) ValidateHeader(header *types.Header, checkPow, uncle bool) error {
+	// Short circuit if the header's already known or its parent missing
+	if sm.bc.HasHeader(header.Hash()) {
+		return nil
+	}
+	if parent := sm.bc.GetHeader(header.ParentHash); parent == nil {
+		return ParentError(header.ParentHash)
+	} else {
+		return ValidateHeader(sm.Pow, header, parent, checkPow, uncle)
+	}
+}
+
 // See YP section 4.3.4. "Block Header Validity"
 // Validates a header. Returns an error if the header is invalid.
 func ValidateHeader(pow pow.PoW, header *types.Header, parent *types.Header, checkPow, uncle bool) error {
 	if big.NewInt(int64(len(header.Extra))).Cmp(params.MaximumExtraDataSize) == 1 {
 		return fmt.Errorf("Header extra data too long (%d)", len(header.Extra))
 	}
-
 	if uncle {
 		if header.Time.Cmp(common.MaxBig) == 1 {
 			return BlockTSTooBigErr
diff --git a/core/blockchain.go b/core/blockchain.go
index 7bfe13a11..48c935eac 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -67,9 +67,9 @@ type BlockChain struct {
 	chainmu sync.RWMutex
 	tsmu    sync.RWMutex
 
-	td              *big.Int
-	currentBlock    *types.Block
-	currentGasLimit *big.Int
+	checkpoint    int           // checkpoint counts towards the new checkpoint
+	currentHeader *types.Header // Current head of the header chain (may be above the block chain!)
+	currentBlock  *types.Block  // Current head of the block chain
 
 	headerCache  *lru.Cache // Cache for the most recent block headers
 	bodyCache    *lru.Cache // Cache for the most recent block bodies
@@ -120,20 +120,15 @@ func NewBlockChain(chainDb ethdb.Database, pow pow.PoW, mux *event.TypeMux) (*Bl
 		}
 		glog.V(logger.Info).Infoln("WARNING: Wrote default ethereum genesis block")
 	}
-	if err := bc.setLastState(); err != nil {
+	if err := bc.loadLastState(); err != nil {
 		return nil, err
 	}
 	// Check the current state of the block hashes and make sure that we do not have any of the bad blocks in our chain
 	for hash, _ := range BadHashes {
-		if block := bc.GetBlock(hash); block != nil {
-			glog.V(logger.Error).Infof("Found bad hash. Reorganising chain to state %x\n", block.ParentHash().Bytes()[:4])
-			block = bc.GetBlock(block.ParentHash())
-			if block == nil {
-				glog.Fatal("Unable to complete. Parent block not found. Corrupted DB?")
-			}
-			bc.SetHead(block)
-
-			glog.V(logger.Error).Infoln("Chain reorg was successfull. Resuming normal operation")
+		if header := bc.GetHeader(hash); header != nil {
+			glog.V(logger.Error).Infof("Found bad hash, rewinding chain to block #%d [%x…]", header.Number, header.ParentHash[:4])
+			bc.SetHead(header.Number.Uint64() - 1)
+			glog.V(logger.Error).Infoln("Chain rewind was successful, resuming normal operation")
 		}
 	}
 	// Take ownership of this particular state
@@ -141,46 +136,104 @@ func NewBlockChain(chainDb ethdb.Database, pow pow.PoW, mux *event.TypeMux) (*Bl
 	return bc, nil
 }
 
-func (bc *BlockChain) SetHead(head *types.Block) {
+// loadLastState loads the last known chain state from the database. This method
+// assumes that the chain manager mutex is held.
+func (self *BlockChain) loadLastState() error {
+	// Restore the last known head block
+	head := GetHeadBlockHash(self.chainDb)
+	if head == (common.Hash{}) {
+		// Corrupt or empty database, init from scratch
+		self.Reset()
+	} else {
+		if block := self.GetBlock(head); block != nil {
+			// Block found, set as the current head
+			self.currentBlock = block
+		} else {
+			// Corrupt or empty database, init from scratch
+			self.Reset()
+		}
+	}
+	// Restore the last known head header
+	self.currentHeader = self.currentBlock.Header()
+	if head := GetHeadHeaderHash(self.chainDb); head != (common.Hash{}) {
+		if header := self.GetHeader(head); header != nil {
+			self.currentHeader = header
+		}
+	}
+	// Issue a status log and return
+	headerTd := self.GetTd(self.currentHeader.Hash())
+	blockTd := self.GetTd(self.currentBlock.Hash())
+
+	glog.V(logger.Info).Infof("Last header: #%d [%x…] TD=%v", self.currentHeader.Number, self.currentHeader.Hash(), headerTd)
+	glog.V(logger.Info).Infof("Last block: #%d [%x…] TD=%v", self.currentBlock.Number(), self.currentBlock.Hash(), blockTd)
+
+	return nil
+}
+
+// SetHead rewind the local chain to a new head entity. In the case of headers,
+// everything above the new head will be deleted and the new one set. In the case
+// of blocks though, the head may be further rewound if block bodies are missing
+// (non-archive nodes after a fast sync).
+func (bc *BlockChain) SetHead(head uint64) {
 	bc.mu.Lock()
 	defer bc.mu.Unlock()
 
-	for block := bc.currentBlock; block != nil && block.Hash() != head.Hash(); block = bc.GetBlock(block.ParentHash()) {
-		DeleteBlock(bc.chainDb, block.Hash())
+	// Delete everything from the current header head (is above block head)
+	for i := bc.currentHeader.Number.Uint64(); i > head; i-- {
+		if hash := GetCanonicalHash(bc.chainDb, i); hash != (common.Hash{}) {
+			DeleteCanonicalHash(bc.chainDb, i)
+			DeleteHeader(bc.chainDb, hash)
+			DeleteBody(bc.chainDb, hash)
+			DeleteTd(bc.chainDb, hash)
+		}
+	}
+	bc.currentHeader = GetHeader(bc.chainDb, GetCanonicalHash(bc.chainDb, head))
+
+	// Rewind the block chain until a whole block is found
+	for bc.GetBlockByNumber(head) == nil {
+		head--
 	}
+	bc.currentBlock = bc.GetBlockByNumber(head)
+
+	// Clear out any stale content from the caches
 	bc.headerCache.Purge()
 	bc.bodyCache.Purge()
 	bc.bodyRLPCache.Purge()
 	bc.blockCache.Purge()
 	bc.futureBlocks.Purge()
 
-	bc.currentBlock = head
-	bc.setTotalDifficulty(bc.GetTd(head.Hash()))
-	bc.insert(head)
-	bc.setLastState()
+	// Update all computed fields to the new head
+	bc.insert(bc.currentBlock)
+	bc.loadLastState()
 }
 
-func (self *BlockChain) Td() *big.Int {
+func (self *BlockChain) GasLimit() *big.Int {
 	self.mu.RLock()
 	defer self.mu.RUnlock()
 
-	return new(big.Int).Set(self.td)
+	return self.currentBlock.GasLimit()
 }
 
-func (self *BlockChain) GasLimit() *big.Int {
+func (self *BlockChain) LastBlockHash() common.Hash {
 	self.mu.RLock()
 	defer self.mu.RUnlock()
 
-	return self.currentBlock.GasLimit()
+	return self.currentBlock.Hash()
 }
 
-func (self *BlockChain) LastBlockHash() common.Hash {
+// CurrentHeader retrieves the current head header of the canonical chain. The
+// header is retrieved from the chain manager's internal cache, involving no
+// database operations.
+func (self *BlockChain) CurrentHeader() *types.Header {
 	self.mu.RLock()
 	defer self.mu.RUnlock()
 
-	return self.currentBlock.Hash()
+	return self.currentHeader
 }
 
+// CurrentBlock retrieves the current head block of the canonical chain. The
+// block is retrieved from the chain manager's internal cache, involving no
+// database operations.
 func (self *BlockChain) CurrentBlock() *types.Block {
 	self.mu.RLock()
 	defer self.mu.RUnlock()
@@ -192,7 +245,7 @@ func (self *BlockChain) Status() (td *big.Int, currentBlock common.Hash, genesis
 	self.mu.RLock()
 	defer self.mu.RUnlock()
 
-	return new(big.Int).Set(self.td), self.currentBlock.Hash(), self.genesisBlock.Hash()
+	return self.GetTd(self.currentBlock.Hash()), self.currentBlock.Hash(), self.genesisBlock.Hash()
 }
 
 func (self *BlockChain) SetProcessor(proc types.BlockProcessor) {
@@ -203,26 +256,6 @@ func (self *BlockChain) State() (*state.StateDB, error) {
 	return state.New(self.CurrentBlock().Root(), self.chainDb)
 }
 
-func (bc *BlockChain) setLastState() error {
-	head := GetHeadBlockHash(bc.chainDb)
-	if head != (common.Hash{}) {
-		block := bc.GetBlock(head)
-		if block != nil {
-			bc.currentBlock = block
-		}
-	} else {
-		bc.Reset()
-	}
-	bc.td = bc.GetTd(bc.currentBlock.Hash())
-	bc.currentGasLimit = CalcGasLimit(bc.currentBlock)
-
-	if glog.V(logger.Info) {
-		glog.Infof("Last block (#%v) %x TD=%v\n", bc.currentBlock.Number(), bc.currentBlock.Hash(), bc.td)
-	}
-
-	return nil
-}
-
 // Reset purges the entire blockchain, restoring it to its genesis state.
 func (bc *BlockChain) Reset() {
 	bc.ResetWithGenesisBlock(bc.genesisBlock)
@@ -238,6 +271,9 @@ func (bc *BlockChain) ResetWithGenesisBlock(genesis *types.Block) {
 	for block := bc.currentBlock; block != nil; block = bc.GetBlock(block.ParentHash()) {
 		DeleteBlock(bc.chainDb, block.Hash())
 	}
+	for header := bc.currentHeader; header != nil; header = bc.GetHeader(header.ParentHash) {
+		DeleteBlock(bc.chainDb, header.Hash())
+	}
 	bc.headerCache.Purge()
 	bc.bodyCache.Purge()
 	bc.bodyRLPCache.Purge()
@@ -254,7 +290,7 @@ func (bc *BlockChain) ResetWithGenesisBlock(genesis *types.Block) {
 	bc.genesisBlock = genesis
 	bc.insert(bc.genesisBlock)
 	bc.currentBlock = bc.genesisBlock
-	bc.setTotalDifficulty(genesis.Difficulty())
+	bc.currentHeader = bc.genesisBlock.Header()
 }
 
 // Export writes the active chain to the given writer.
@@ -290,17 +326,26 @@ func (self *BlockChain) ExportN(w io.Writer, first uint64, last uint64) error {
 	return nil
 }
 
-// insert injects a block into the current chain block chain. Note, this function
-// assumes that the `mu` mutex is held!
+// insert injects a new head block into the current block chain. This method
+// assumes that the block is indeed a true head. It will also reset the head
+// header to this very same block to prevent the headers from diverging on a
+// different header chain.
+//
+// Note, this function assumes that the `mu` mutex is held!
 func (bc *BlockChain) insert(block *types.Block) {
 	// Add the block to the canonical chain number scheme and mark as the head
 	if err := WriteCanonicalHash(bc.chainDb, block.Hash(), block.NumberU64()); err != nil {
 		glog.Fatalf("failed to insert block number: %v", err)
 	}
 	if err := WriteHeadBlockHash(bc.chainDb, block.Hash()); err != nil {
-		glog.Fatalf("failed to insert block number: %v", err)
+		glog.Fatalf("failed to insert head block hash: %v", err)
 	}
+	if err := WriteHeadHeaderHash(bc.chainDb, block.Hash()); err != nil {
+		glog.Fatalf("failed to insert head header hash: %v", err)
+	}
+	// Update the internal state with the head block
 	bc.currentBlock = block
+	bc.currentHeader = block.Header()
 }
 
 // Accessors
@@ -456,19 +501,15 @@ func (self *BlockChain) GetBlocksFromHash(hash common.Hash, n int) (blocks []*ty
 	return
 }
 
-func (self *BlockChain) GetUnclesInChain(block *types.Block, length int) (uncles []*types.Header) {
+// GetUnclesInChain retrieves all the uncles from a given block backwards until
+// a specific distance is reached.
+func (self *BlockChain) GetUnclesInChain(block *types.Block, length int) []*types.Header {
+	uncles := []*types.Header{}
 	for i := 0; block != nil && i < length; i++ {
 		uncles = append(uncles, block.Uncles()...)
 		block = self.GetBlock(block.ParentHash())
 	}
-
-	return
-}
-
-// setTotalDifficulty updates the TD of the chain manager. Note, this function
-// assumes that the `mu` mutex is held!
-func (bc *BlockChain) setTotalDifficulty(td *big.Int) {
-	bc.td = new(big.Int).Set(td)
+	return uncles
 }
 
 func (bc *BlockChain) Stop() {
@@ -504,6 +545,135 @@ const (
 	SideStatTy
 )
 
+// writeHeader writes a header into the local chain, given that its parent is
+// already known. If the total difficulty of the newly inserted header becomes
+// greater than the old known TD, the canonical chain is re-routed.
+//
+// Note: This method is not concurrent-safe with inserting blocks simultaneously
+// into the chain, as side effects caused by reorganizations cannot be emulated
+// without the real blocks. Hence, writing headers directly should only be done
+// in two scenarios: pure-header mode of operation (light clients), or properly
+// separated header/block phases (non-archive clients).
+func (self *BlockChain) writeHeader(header *types.Header) error {
+	self.wg.Add(1)
+	defer self.wg.Done()
+
+	// Calculate the total difficulty of the header
+	ptd := self.GetTd(header.ParentHash)
+	if ptd == nil {
+		return ParentError(header.ParentHash)
+	}
+	td := new(big.Int).Add(header.Difficulty, ptd)
+
+	// Make sure no inconsistent state is leaked during insertion
+	self.mu.Lock()
+	defer self.mu.Unlock()
+
+	// If the total difficulty is higher than our known, add it to the canonical chain
+	if td.Cmp(self.GetTd(self.currentHeader.Hash())) > 0 {
+		// Delete any canonical number assignments above the new head
+		for i := header.Number.Uint64() + 1; GetCanonicalHash(self.chainDb, i) != (common.Hash{}); i++ {
+			DeleteCanonicalHash(self.chainDb, i)
+		}
+		// Overwrite any stale canonical number assignments
+		head := self.GetHeader(header.ParentHash)
+		for GetCanonicalHash(self.chainDb, head.Number.Uint64()) != head.Hash() {
+			WriteCanonicalHash(self.chainDb, head.Hash(), head.Number.Uint64())
+			head = self.GetHeader(head.ParentHash)
+		}
+		// Extend the canonical chain with the new header
+		if err := WriteCanonicalHash(self.chainDb, header.Hash(), header.Number.Uint64()); err != nil {
+			glog.Fatalf("failed to insert header number: %v", err)
+		}
+		if err := WriteHeadHeaderHash(self.chainDb, header.Hash()); err != nil {
+			glog.Fatalf("failed to insert head header hash: %v", err)
+		}
+		self.currentHeader = types.CopyHeader(header)
+	}
+	// Irrelevant of the canonical status, write the header itself to the database
+	if err := WriteTd(self.chainDb, header.Hash(), td); err != nil {
+		glog.Fatalf("failed to write header total difficulty: %v", err)
+	}
+	if err := WriteHeader(self.chainDb, header); err != nil {
+		glog.Fatalf("filed to write header contents: %v", err)
+	}
+	return nil
+}
+
+// InsertHeaderChain will attempt to insert the given header chain in to the
+// local chain, possibly creating a dork. If an error is returned,  it will
+// return the index number of the failing header as well an error describing
+// what went wrong.
+//
+// The verify parameter can be used to fine tune whether nonce verification
+// should be done or not. The reason behind the optional check is because some
+// of the header retrieval mechanisms already need to verfy nonces, as well as
+// because nonces can be verified sparsely, not needing to check each.
+func (self *BlockChain) InsertHeaderChain(chain []*types.Header, verify bool) (int, error) {
+	self.wg.Add(1)
+	defer self.wg.Done()
+
+	// Make sure only one thread manipulates the chain at once
+	self.chainmu.Lock()
+	defer self.chainmu.Unlock()
+
+	// Collect some import statistics to report on
+	stats := struct{ processed, ignored int }{}
+	start := time.Now()
+
+	// Start the parallel nonce verifier, with a fake nonce if not requested
+	verifier := self.pow
+	if !verify {
+		verifier = FakePow{}
+	}
+	nonceAbort, nonceResults := verifyNoncesFromHeaders(verifier, chain)
+	defer close(nonceAbort)
+
+	// Iterate over the headers, inserting any new ones
+	complete := make([]bool, len(chain))
+	for i, header := range chain {
+		// Short circuit insertion if shutting down
+		if atomic.LoadInt32(&self.procInterrupt) == 1 {
+			glog.V(logger.Debug).Infoln("Premature abort during header chain processing")
+			break
+		}
+		hash := header.Hash()
+
+		// Accumulate verification results until the next header is verified
+		for !complete[i] {
+			if res := <-nonceResults; res.valid {
+				complete[res.index] = true
+			} else {
+				header := chain[res.index]
+				return res.index, &BlockNonceErr{
+					Hash:   header.Hash(),
+					Number: new(big.Int).Set(header.Number),
+					Nonce:  header.Nonce.Uint64(),
+				}
+			}
+		}
+		if BadHashes[hash] {
+			glog.V(logger.Error).Infof("Bad header %d [%x…], known bad hash", header.Number, hash)
+			return i, BadHashError(hash)
+		}
+		// Write the header to the chain and get the status
+		if self.HasHeader(hash) {
+			stats.ignored++
+			continue
+		}
+		if err := self.writeHeader(header); err != nil {
+			return i, err
+		}
+		stats.processed++
+	}
+	// Report some public statistics so the user has a clue what's going on
+	first, last := chain[0], chain[len(chain)-1]
+	glog.V(logger.Info).Infof("imported %d header(s) (%d ignored) in %v. #%v [%x… / %x…]", stats.processed, stats.ignored,
+		time.Since(start), last.Number, first.Hash().Bytes()[:4], last.Hash().Bytes()[:4])
+
+	return 0, nil
+}
+
 // WriteBlock writes the block to the chain.
 func (self *BlockChain) WriteBlock(block *types.Block) (status writeStatus, err error) {
 	self.wg.Add(1)
@@ -522,7 +692,7 @@ func (self *BlockChain) WriteBlock(block *types.Block) (status writeStatus, err
 
 	// Compare the TD of the last known block in the canonical chain to make sure it's greater.
 	// At this point it's possible that a different chain (fork) becomes the new canonical chain.
-	if td.Cmp(self.Td()) > 0 {
+	if td.Cmp(self.GetTd(self.currentBlock.Hash())) > 0 {
 		// chain fork
 		if block.ParentHash() != cblock.Hash() {
 			// during split we merge two different chains and create the new canonical chain
@@ -534,7 +704,6 @@ func (self *BlockChain) WriteBlock(block *types.Block) (status writeStatus, err
 		status = CanonStatTy
 
 		self.mu.Lock()
-		self.setTotalDifficulty(td)
 		self.insert(block)
 		self.mu.Unlock()
 	} else {
@@ -580,7 +749,7 @@ func (self *BlockChain) InsertChain(chain types.Blocks) (int, error) {
 	txcount := 0
 	for i, block := range chain {
 		if atomic.LoadInt32(&self.procInterrupt) == 1 {
-			glog.V(logger.Debug).Infoln("Premature abort during chain processing")
+			glog.V(logger.Debug).Infoln("Premature abort during block chain processing")
 			break
 		}
 
@@ -788,8 +957,7 @@ func (self *BlockChain) postChainEvents(events []interface{}) {
 		if event, ok := event.(ChainEvent); ok {
 			// We need some control over the mining operation. Acquiring locks and waiting for the miner to create new block takes too long
 			// and in most cases isn't even necessary.
-			if self.currentBlock.Hash() == event.Hash {
-				self.currentGasLimit = CalcGasLimit(event.Block)
+			if self.LastBlockHash() == event.Hash {
 				self.eventMux.Post(ChainHeadEvent{event.Block})
 			}
 		}
diff --git a/core/blockchain_test.go b/core/blockchain_test.go
index 13971ccba..4d0f13ef1 100644
--- a/core/blockchain_test.go
+++ b/core/blockchain_test.go
@@ -64,44 +64,58 @@ func theBlockChain(db ethdb.Database, t *testing.T) *BlockChain {
 }
 
 // Test fork of length N starting from block i
-func testFork(t *testing.T, bman *BlockProcessor, i, N int, f func(td1, td2 *big.Int)) {
-	// switch databases to process the new chain
-	db, err := ethdb.NewMemDatabase()
-	if err != nil {
-		t.Fatal("Failed to create db:", err)
-	}
-	// copy old chain up to i into new db with deterministic canonical
-	bman2, err := newCanonical(i, db)
+func testFork(t *testing.T, processor *BlockProcessor, i, n int, full bool, comparator func(td1, td2 *big.Int)) {
+	// Copy old chain up to #i into a new db
+	db, processor2, err := newCanonical(i, full)
 	if err != nil {
 		t.Fatal("could not make new canonical in testFork", err)
 	}
-	// assert the bmans have the same block at i
-	bi1 := bman.bc.GetBlockByNumber(uint64(i)).Hash()
-	bi2 := bman2.bc.GetBlockByNumber(uint64(i)).Hash()
-	if bi1 != bi2 {
-		fmt.Printf("%+v\n%+v\n\n", bi1, bi2)
-		t.Fatal("chains do not have the same hash at height", i)
+	// Assert the chains have the same header/block at #i
+	var hash1, hash2 common.Hash
+	if full {
+		hash1 = processor.bc.GetBlockByNumber(uint64(i)).Hash()
+		hash2 = processor2.bc.GetBlockByNumber(uint64(i)).Hash()
+	} else {
+		hash1 = processor.bc.GetHeaderByNumber(uint64(i)).Hash()
+		hash2 = processor2.bc.GetHeaderByNumber(uint64(i)).Hash()
 	}
-	bman2.bc.SetProcessor(bman2)
-
-	// extend the fork
-	parent := bman2.bc.CurrentBlock()
-	chainB := makeChain(parent, N, db, forkSeed)
-	_, err = bman2.bc.InsertChain(chainB)
-	if err != nil {
-		t.Fatal("Insert chain error for fork:", err)
+	if hash1 != hash2 {
+		t.Errorf("chain content mismatch at %d: have hash %v, want hash %v", i, hash2, hash1)
 	}
-
-	tdpre := bman.bc.Td()
-	// Test the fork's blocks on the original chain
-	td, err := testChain(chainB, bman)
-	if err != nil {
-		t.Fatal("expected chainB not to give errors:", err)
+	// Extend the newly created chain
+	var (
+		blockChainB  []*types.Block
+		headerChainB []*types.Header
+	)
+	if full {
+		blockChainB = makeBlockChain(processor2.bc.CurrentBlock(), n, db, forkSeed)
+		if _, err := processor2.bc.InsertChain(blockChainB); err != nil {
+			t.Fatalf("failed to insert forking chain: %v", err)
+		}
+	} else {
+		headerChainB = makeHeaderChain(processor2.bc.CurrentHeader(), n, db, forkSeed)
+		if _, err := processor2.bc.InsertHeaderChain(headerChainB, true); err != nil {
+			t.Fatalf("failed to insert forking chain: %v", err)
+		}
 	}
-	// Compare difficulties
-	f(tdpre, td)
+	// Sanity check that the forked chain can be imported into the original
+	var tdPre, tdPost *big.Int
 
-	// Loop over parents making sure reconstruction is done properly
+	if full {
+		tdPre = processor.bc.GetTd(processor.bc.CurrentBlock().Hash())
+		if err := testBlockChainImport(blockChainB, processor); err != nil {
+			t.Fatalf("failed to import forked block chain: %v", err)
+		}
+		tdPost = processor.bc.GetTd(blockChainB[len(blockChainB)-1].Hash())
+	} else {
+		tdPre = processor.bc.GetTd(processor.bc.CurrentHeader().Hash())
+		if err := testHeaderChainImport(headerChainB, processor); err != nil {
+			t.Fatalf("failed to import forked header chain: %v", err)
+		}
+		tdPost = processor.bc.GetTd(headerChainB[len(headerChainB)-1].Hash())
+	}
+	// Compare the total difficulties of the chains
+	comparator(tdPre, tdPost)
 }
 
 func printChain(bc *BlockChain) {
@@ -111,22 +125,41 @@ func printChain(bc *BlockChain) {
 	}
 }
 
-// process blocks against a chain
-func testChain(chainB types.Blocks, bman *BlockProcessor) (*big.Int, error) {
-	for _, block := range chainB {
-		_, _, err := bman.bc.processor.Process(block)
-		if err != nil {
+// testBlockChainImport tries to process a chain of blocks, writing them into
+// the database if successful.
+func testBlockChainImport(chain []*types.Block, processor *BlockProcessor) error {
+	for _, block := range chain {
+		// Try and process the block
+		if _, _, err := processor.Process(block); err != nil {
 			if IsKnownBlockErr(err) {
 				continue
 			}
-			return nil, err
+			return err
 		}
-		bman.bc.mu.Lock()
-		WriteTd(bman.bc.chainDb, block.Hash(), new(big.Int).Add(block.Difficulty(), bman.bc.GetTd(block.ParentHash())))
-		WriteBlock(bman.bc.chainDb, block)
-		bman.bc.mu.Unlock()
+		// Manually insert the block into the database, but don't reorganize (allows subsequent testing)
+		processor.bc.mu.Lock()
+		WriteTd(processor.chainDb, block.Hash(), new(big.Int).Add(block.Difficulty(), processor.bc.GetTd(block.ParentHash())))
+		WriteBlock(processor.chainDb, block)
+		processor.bc.mu.Unlock()
 	}
-	return bman.bc.GetTd(chainB[len(chainB)-1].Hash()), nil
+	return nil
+}
+
+// testHeaderChainImport tries to process a chain of header, writing them into
+// the database if successful.
+func testHeaderChainImport(chain []*types.Header, processor *BlockProcessor) error {
+	for _, header := range chain {
+		// Try and validate the header
+		if err := processor.ValidateHeader(header, false, false); err != nil {
+			return err
+		}
+		// Manually insert the header into the database, but don't reorganize (allows subsequent testing)
+		processor.bc.mu.Lock()
+		WriteTd(processor.chainDb, header.Hash(), new(big.Int).Add(header.Difficulty, processor.bc.GetTd(header.ParentHash)))
+		WriteHeader(processor.chainDb, header)
+		processor.bc.mu.Unlock()
+	}
+	return nil
 }
 
 func loadChain(fn string, t *testing.T) (types.Blocks, error) {
@@ -154,139 +187,147 @@ func insertChain(done chan bool, blockchain *BlockChain, chain types.Blocks, t *
 }
 
 func TestLastBlock(t *testing.T) {
-	db, err := ethdb.NewMemDatabase()
-	if err != nil {
-		t.Fatal("Failed to create db:", err)
-	}
+	db, _ := ethdb.NewMemDatabase()
+
 	bchain := theBlockChain(db, t)
-	block := makeChain(bchain.CurrentBlock(), 1, db, 0)[0]
+	block := makeBlockChain(bchain.CurrentBlock(), 1, db, 0)[0]
 	bchain.insert(block)
 	if block.Hash() != GetHeadBlockHash(db) {
 		t.Errorf("Write/Get HeadBlockHash failed")
 	}
 }
 
-func TestExtendCanonical(t *testing.T) {
-	CanonicalLength := 5
-	db, err := ethdb.NewMemDatabase()
-	if err != nil {
-		t.Fatal("Failed to create db:", err)
-	}
-	// make first chain starting from genesis
-	bman, err := newCanonical(CanonicalLength, db)
+// Tests that given a starting canonical chain of a given size, it can be extended
+// with various length chains.
+func TestExtendCanonicalHeaders(t *testing.T) { testExtendCanonical(t, false) }
+func TestExtendCanonicalBlocks(t *testing.T)  { testExtendCanonical(t, true) }
+
+func testExtendCanonical(t *testing.T, full bool) {
+	length := 5
+
+	// Make first chain starting from genesis
+	_, processor, err := newCanonical(length, full)
 	if err != nil {
-		t.Fatal("Could not make new canonical chain:", err)
+		t.Fatalf("failed to make new canonical chain: %v", err)
 	}
-	f := func(td1, td2 *big.Int) {
+	// Define the difficulty comparator
+	better := func(td1, td2 *big.Int) {
 		if td2.Cmp(td1) <= 0 {
-			t.Error("expected chainB to have higher difficulty. Got", td2, "expected more than", td1)
+			t.Errorf("total difficulty mismatch: have %v, expected more than %v", td2, td1)
 		}
 	}
-	// Start fork from current height (CanonicalLength)
-	testFork(t, bman, CanonicalLength, 1, f)
-	testFork(t, bman, CanonicalLength, 2, f)
-	testFork(t, bman, CanonicalLength, 5, f)
-	testFork(t, bman, CanonicalLength, 10, f)
+	// Start fork from current height
+	testFork(t, processor, length, 1, full, better)
+	testFork(t, processor, length, 2, full, better)
+	testFork(t, processor, length, 5, full, better)
+	testFork(t, processor, length, 10, full, better)
 }
 
-func TestShorterFork(t *testing.T) {
-	db, err := ethdb.NewMemDatabase()
-	if err != nil {
-		t.Fatal("Failed to create db:", err)
-	}
-	// make first chain starting from genesis
-	bman, err := newCanonical(10, db)
+// Tests that given a starting canonical chain of a given size, creating shorter
+// forks do not take canonical ownership.
+func TestShorterForkHeaders(t *testing.T) { testShorterFork(t, false) }
+func TestShorterForkBlocks(t *testing.T)  { testShorterFork(t, true) }
+
+func testShorterFork(t *testing.T, full bool) {
+	length := 10
+
+	// Make first chain starting from genesis
+	_, processor, err := newCanonical(length, full)
 	if err != nil {
-		t.Fatal("Could not make new canonical chain:", err)
+		t.Fatalf("failed to make new canonical chain: %v", err)
 	}
-	f := func(td1, td2 *big.Int) {
+	// Define the difficulty comparator
+	worse := func(td1, td2 *big.Int) {
 		if td2.Cmp(td1) >= 0 {
-			t.Error("expected chainB to have lower difficulty. Got", td2, "expected less than", td1)
+			t.Errorf("total difficulty mismatch: have %v, expected less than %v", td2, td1)
 		}
 	}
-	// Sum of numbers must be less than 10
-	// for this to be a shorter fork
-	testFork(t, bman, 0, 3, f)
-	testFork(t, bman, 0, 7, f)
-	testFork(t, bman, 1, 1, f)
-	testFork(t, bman, 1, 7, f)
-	testFork(t, bman, 5, 3, f)
-	testFork(t, bman, 5, 4, f)
+	// Sum of numbers must be less than `length` for this to be a shorter fork
+	testFork(t, processor, 0, 3, full, worse)
+	testFork(t, processor, 0, 7, full, worse)
+	testFork(t, processor, 1, 1, full, worse)
+	testFork(t, processor, 1, 7, full, worse)
+	testFork(t, processor, 5, 3, full, worse)
+	testFork(t, processor, 5, 4, full, worse)
 }
 
-func TestLongerFork(t *testing.T) {
-	db, err := ethdb.NewMemDatabase()
-	if err != nil {
-		t.Fatal("Failed to create db:", err)
-	}
-	// make first chain starting from genesis
-	bman, err := newCanonical(10, db)
+// Tests that given a starting canonical chain of a given size, creating longer
+// forks do take canonical ownership.
+func TestLongerForkHeaders(t *testing.T) { testLongerFork(t, false) }
+func TestLongerForkBlocks(t *testing.T)  { testLongerFork(t, true) }
+
+func testLongerFork(t *testing.T, full bool) {
+	length := 10
+
+	// Make first chain starting from genesis
+	_, processor, err := newCanonical(length, full)
 	if err != nil {
-		t.Fatal("Could not make new canonical chain:", err)
+		t.Fatalf("failed to make new canonical chain: %v", err)
 	}
-	f := func(td1, td2 *big.Int) {
+	// Define the difficulty comparator
+	better := func(td1, td2 *big.Int) {
 		if td2.Cmp(td1) <= 0 {
-			t.Error("expected chainB to have higher difficulty. Got", td2, "expected more than", td1)
+			t.Errorf("total difficulty mismatch: have %v, expected more than %v", td2, td1)
 		}
 	}
-	// Sum of numbers must be greater than 10
-	// for this to be a longer fork
-	testFork(t, bman, 0, 11, f)
-	testFork(t, bman, 0, 15, f)
-	testFork(t, bman, 1, 10, f)
-	testFork(t, bman, 1, 12, f)
-	testFork(t, bman, 5, 6, f)
-	testFork(t, bman, 5, 8, f)
+	// Sum of numbers must be greater than `length` for this to be a longer fork
+	testFork(t, processor, 0, 11, full, better)
+	testFork(t, processor, 0, 15, full, better)
+	testFork(t, processor, 1, 10, full, better)
+	testFork(t, processor, 1, 12, full, better)
+	testFork(t, processor, 5, 6, full, better)
+	testFork(t, processor, 5, 8, full, better)
 }
 
-func TestEqualFork(t *testing.T) {
-	db, err := ethdb.NewMemDatabase()
-	if err != nil {
-		t.Fatal("Failed to create db:", err)
-	}
-	bman, err := newCanonical(10, db)
+// Tests that given a starting canonical chain of a given size, creating equal
+// forks do take canonical ownership.
+func TestEqualForkHeaders(t *testing.T) { testEqualFork(t, false) }
+func TestEqualForkBlocks(t *testing.T)  { testEqualFork(t, true) }
+
+func testEqualFork(t *testing.T, full bool) {
+	length := 10
+
+	// Make first chain starting from genesis
+	_, processor, err := newCanonical(length, full)
 	if err != nil {
-		t.Fatal("Could not make new canonical chain:", err)
+		t.Fatalf("failed to make new canonical chain: %v", err)
 	}
-	f := func(td1, td2 *big.Int) {
+	// Define the difficulty comparator
+	equal := func(td1, td2 *big.Int) {
 		if td2.Cmp(td1) != 0 {
-			t.Error("expected chainB to have equal difficulty. Got", td2, "expected ", td1)
+			t.Errorf("total difficulty mismatch: have %v, want %v", td2, td1)
 		}
 	}
-	// Sum of numbers must be equal to 10
-	// for this to be an equal fork
-	testFork(t, bman, 0, 10, f)
-	testFork(t, bman, 1, 9, f)
-	testFork(t, bman, 2, 8, f)
-	testFork(t, bman, 5, 5, f)
-	testFork(t, bman, 6, 4, f)
-	testFork(t, bman, 9, 1, f)
+	// Sum of numbers must be equal to `length` for this to be an equal fork
+	testFork(t, processor, 0, 10, full, equal)
+	testFork(t, processor, 1, 9, full, equal)
+	testFork(t, processor, 2, 8, full, equal)
+	testFork(t, processor, 5, 5, full, equal)
+	testFork(t, processor, 6, 4, full, equal)
+	testFork(t, processor, 9, 1, full, equal)
 }
 
-func TestBrokenChain(t *testing.T) {
-	db, err := ethdb.NewMemDatabase()
-	if err != nil {
-		t.Fatal("Failed to create db:", err)
-	}
-	bman, err := newCanonical(10, db)
-	if err != nil {
-		t.Fatal("Could not make new canonical chain:", err)
-	}
-	db2, err := ethdb.NewMemDatabase()
-	if err != nil {
-		t.Fatal("Failed to create db:", err)
-	}
-	bman2, err := newCanonical(10, db2)
+// Tests that chains missing links do not get accepted by the processor.
+func TestBrokenHeaderChain(t *testing.T) { testBrokenChain(t, false) }
+func TestBrokenBlockChain(t *testing.T)  { testBrokenChain(t, true) }
+
+func testBrokenChain(t *testing.T, full bool) {
+	// Make chain starting from genesis
+	db, processor, err := newCanonical(10, full)
 	if err != nil {
-		t.Fatal("Could not make new canonical chain:", err)
+		t.Fatalf("failed to make new canonical chain: %v", err)
 	}
-	bman2.bc.SetProcessor(bman2)
-	parent := bman2.bc.CurrentBlock()
-	chainB := makeChain(parent, 5, db2, forkSeed)
-	chainB = chainB[1:]
-	_, err = testChain(chainB, bman)
-	if err == nil {
-		t.Error("expected broken chain to return error")
+	// Create a forked chain, and try to insert with a missing link
+	if full {
+		chain := makeBlockChain(processor.bc.CurrentBlock(), 5, db, forkSeed)[1:]
+		if err := testBlockChainImport(chain, processor); err == nil {
+			t.Errorf("broken block chain not reported")
+		}
+	} else {
+		chain := makeHeaderChain(processor.bc.CurrentHeader(), 5, db, forkSeed)[1:]
+		if err := testHeaderChainImport(chain, processor); err == nil {
+			t.Errorf("broken header chain not reported")
+		}
 	}
 }
 
@@ -376,7 +417,16 @@ type bproc struct{}
 
 func (bproc) Process(*types.Block) (vm.Logs, types.Receipts, error) { return nil, nil, nil }
 
-func makeChainWithDiff(genesis *types.Block, d []int, seed byte) []*types.Block {
+func makeHeaderChainWithDiff(genesis *types.Block, d []int, seed byte) []*types.Header {
+	blocks := makeBlockChainWithDiff(genesis, d, seed)
+	headers := make([]*types.Header, len(blocks))
+	for i, block := range blocks {
+		headers[i] = block.Header()
+	}
+	return headers
+}
+
+func makeBlockChainWithDiff(genesis *types.Block, d []int, seed byte) []*types.Block {
 	var chain []*types.Block
 	for i, difficulty := range d {
 		header := &types.Header{
@@ -410,142 +460,209 @@ func chm(genesis *types.Block, db ethdb.Database) *BlockChain {
 	return bc
 }
 
-func TestReorgLongest(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+// Tests that reorganizing a long difficult chain after a short easy one
+// overwrites the canonical numbers and links in the database.
+func TestReorgLongHeaders(t *testing.T) { testReorgLong(t, false) }
+func TestReorgLongBlocks(t *testing.T)  { testReorgLong(t, true) }
 
-	genesis, err := WriteTestNetGenesisBlock(db, 0)
-	if err != nil {
-		t.Error(err)
-		t.FailNow()
-	}
-	bc := chm(genesis, db)
+func testReorgLong(t *testing.T, full bool) {
+	testReorg(t, []int{1, 2, 4}, []int{1, 2, 3, 4}, 10, full)
+}
 
-	chain1 := makeChainWithDiff(genesis, []int{1, 2, 4}, 10)
-	chain2 := makeChainWithDiff(genesis, []int{1, 2, 3, 4}, 11)
+// Tests that reorganizing a short difficult chain after a long easy one
+// overwrites the canonical numbers and links in the database.
+func TestReorgShortHeaders(t *testing.T) { testReorgShort(t, false) }
+func TestReorgShortBlocks(t *testing.T)  { testReorgShort(t, true) }
 
-	bc.InsertChain(chain1)
-	bc.InsertChain(chain2)
+func testReorgShort(t *testing.T, full bool) {
+	testReorg(t, []int{1, 2, 3, 4}, []int{1, 10}, 11, full)
+}
 
-	prev := bc.CurrentBlock()
-	for block := bc.GetBlockByNumber(bc.CurrentBlock().NumberU64() - 1); block.NumberU64() != 0; prev, block = block, bc.GetBlockByNumber(block.NumberU64()-1) {
-		if prev.ParentHash() != block.Hash() {
-			t.Errorf("parent hash mismatch %x - %x", prev.ParentHash(), block.Hash())
+func testReorg(t *testing.T, first, second []int, td int64, full bool) {
+	// Create a pristine block chain
+	db, _ := ethdb.NewMemDatabase()
+	genesis, _ := WriteTestNetGenesisBlock(db, 0)
+	bc := chm(genesis, db)
+
+	// Insert an easy and a difficult chain afterwards
+	if full {
+		bc.InsertChain(makeBlockChainWithDiff(genesis, first, 11))
+		bc.InsertChain(makeBlockChainWithDiff(genesis, second, 22))
+	} else {
+		bc.InsertHeaderChain(makeHeaderChainWithDiff(genesis, first, 11), false)
+		bc.InsertHeaderChain(makeHeaderChainWithDiff(genesis, second, 22), false)
+	}
+	// Check that the chain is valid number and link wise
+	if full {
+		prev := bc.CurrentBlock()
+		for block := bc.GetBlockByNumber(bc.CurrentBlock().NumberU64() - 1); block.NumberU64() != 0; prev, block = block, bc.GetBlockByNumber(block.NumberU64()-1) {
+			if prev.ParentHash() != block.Hash() {
+				t.Errorf("parent block hash mismatch: have %x, want %x", prev.ParentHash(), block.Hash())
+			}
+		}
+	} else {
+		prev := bc.CurrentHeader()
+		for header := bc.GetHeaderByNumber(bc.CurrentHeader().Number.Uint64() - 1); header.Number.Uint64() != 0; prev, header = header, bc.GetHeaderByNumber(header.Number.Uint64()-1) {
+			if prev.ParentHash != header.Hash() {
+				t.Errorf("parent header hash mismatch: have %x, want %x", prev.ParentHash, header.Hash())
+			}
+		}
+	}
+	// Make sure the chain total difficulty is the correct one
+	want := new(big.Int).Add(genesis.Difficulty(), big.NewInt(td))
+	if full {
+		if have := bc.GetTd(bc.CurrentBlock().Hash()); have.Cmp(want) != 0 {
+			t.Errorf("total difficulty mismatch: have %v, want %v", have, want)
+		}
+	} else {
+		if have := bc.GetTd(bc.CurrentHeader().Hash()); have.Cmp(want) != 0 {
+			t.Errorf("total difficulty mismatch: have %v, want %v", have, want)
 		}
 	}
 }
 
-func TestBadHashes(t *testing.T) {
+// Tests that the insertion functions detect banned hashes.
+func TestBadHeaderHashes(t *testing.T) { testBadHashes(t, false) }
+func TestBadBlockHashes(t *testing.T)  { testBadHashes(t, true) }
+
+func testBadHashes(t *testing.T, full bool) {
+	// Create a pristine block chain
 	db, _ := ethdb.NewMemDatabase()
-	genesis, err := WriteTestNetGenesisBlock(db, 0)
-	if err != nil {
-		t.Error(err)
-		t.FailNow()
-	}
+	genesis, _ := WriteTestNetGenesisBlock(db, 0)
 	bc := chm(genesis, db)
 
-	chain := makeChainWithDiff(genesis, []int{1, 2, 4}, 10)
-	BadHashes[chain[2].Header().Hash()] = true
-
-	_, err = bc.InsertChain(chain)
+	// Create a chain, ban a hash and try to import
+	var err error
+	if full {
+		blocks := makeBlockChainWithDiff(genesis, []int{1, 2, 4}, 10)
+		BadHashes[blocks[2].Header().Hash()] = true
+		_, err = bc.InsertChain(blocks)
+	} else {
+		headers := makeHeaderChainWithDiff(genesis, []int{1, 2, 4}, 10)
+		BadHashes[headers[2].Hash()] = true
+		_, err = bc.InsertHeaderChain(headers, true)
+	}
 	if !IsBadHashError(err) {
 		t.Errorf("error mismatch: want: BadHashError, have: %v", err)
 	}
 }
 
-func TestReorgBadHashes(t *testing.T) {
+// Tests that bad hashes are detected on boot, and the chan rolled back to a
+// good state prior to the bad hash.
+func TestReorgBadHeaderHashes(t *testing.T) { testReorgBadHashes(t, false) }
+func TestReorgBadBlockHashes(t *testing.T)  { testReorgBadHashes(t, true) }
+
+func testReorgBadHashes(t *testing.T, full bool) {
+	// Create a pristine block chain
 	db, _ := ethdb.NewMemDatabase()
-	genesis, err := WriteTestNetGenesisBlock(db, 0)
-	if err != nil {
-		t.Error(err)
-		t.FailNow()
-	}
+	genesis, _ := WriteTestNetGenesisBlock(db, 0)
 	bc := chm(genesis, db)
 
-	chain := makeChainWithDiff(genesis, []int{1, 2, 3, 4}, 11)
-	bc.InsertChain(chain)
-
-	if chain[3].Header().Hash() != bc.LastBlockHash() {
-		t.Errorf("last block hash mismatch: want: %x, have: %x", chain[3].Header().Hash(), bc.LastBlockHash())
-	}
-
-	// NewChainManager should check BadHashes when loading it db
-	BadHashes[chain[3].Header().Hash()] = true
-
-	var eventMux event.TypeMux
-	ncm, err := NewBlockChain(db, FakePow{}, &eventMux)
-	if err != nil {
-		t.Errorf("NewChainManager err: %s", err)
-	}
-
-	// check it set head to (valid) parent of bad hash block
-	if chain[2].Header().Hash() != ncm.LastBlockHash() {
-		t.Errorf("last block hash mismatch: want: %x, have: %x", chain[2].Header().Hash(), ncm.LastBlockHash())
-	}
+	// Create a chain, import and ban aferwards
+	headers := makeHeaderChainWithDiff(genesis, []int{1, 2, 3, 4}, 10)
+	blocks := makeBlockChainWithDiff(genesis, []int{1, 2, 3, 4}, 10)
 
-	if chain[2].Header().GasLimit.Cmp(ncm.GasLimit()) != 0 {
-		t.Errorf("current block gasLimit mismatch: want: %x, have: %x", chain[2].Header().GasLimit, ncm.GasLimit())
+	if full {
+		if _, err := bc.InsertChain(blocks); err != nil {
+			t.Fatalf("failed to import blocks: %v", err)
+		}
+		if bc.CurrentBlock().Hash() != blocks[3].Hash() {
+			t.Errorf("last block hash mismatch: have: %x, want %x", bc.CurrentBlock().Hash(), blocks[3].Header().Hash())
+		}
+		BadHashes[blocks[3].Header().Hash()] = true
+		defer func() { delete(BadHashes, blocks[3].Header().Hash()) }()
+	} else {
+		if _, err := bc.InsertHeaderChain(headers, true); err != nil {
+			t.Fatalf("failed to import headers: %v", err)
+		}
+		if bc.CurrentHeader().Hash() != headers[3].Hash() {
+			t.Errorf("last header hash mismatch: have: %x, want %x", bc.CurrentHeader().Hash(), headers[3].Hash())
+		}
+		BadHashes[headers[3].Hash()] = true
+		defer func() { delete(BadHashes, headers[3].Hash()) }()
 	}
-}
-
-func TestReorgShortest(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
-	genesis, err := WriteTestNetGenesisBlock(db, 0)
+	// Create a new chain manager and check it rolled back the state
+	ncm, err := NewBlockChain(db, FakePow{}, new(event.TypeMux))
 	if err != nil {
-		t.Error(err)
-		t.FailNow()
+		t.Fatalf("failed to create new chain manager: %v", err)
 	}
-	bc := chm(genesis, db)
-
-	chain1 := makeChainWithDiff(genesis, []int{1, 2, 3, 4}, 10)
-	chain2 := makeChainWithDiff(genesis, []int{1, 10}, 11)
-
-	bc.InsertChain(chain1)
-	bc.InsertChain(chain2)
-
-	prev := bc.CurrentBlock()
-	for block := bc.GetBlockByNumber(bc.CurrentBlock().NumberU64() - 1); block.NumberU64() != 0; prev, block = block, bc.GetBlockByNumber(block.NumberU64()-1) {
-		if prev.ParentHash() != block.Hash() {
-			t.Errorf("parent hash mismatch %x - %x", prev.ParentHash(), block.Hash())
+	if full {
+		if ncm.CurrentBlock().Hash() != blocks[2].Header().Hash() {
+			t.Errorf("last block hash mismatch: have: %x, want %x", ncm.CurrentBlock().Hash(), blocks[2].Header().Hash())
+		}
+		if blocks[2].Header().GasLimit.Cmp(ncm.GasLimit()) != 0 {
+			t.Errorf("last  block gasLimit mismatch: have: %x, want %x", ncm.GasLimit(), blocks[2].Header().GasLimit)
+		}
+	} else {
+		if ncm.CurrentHeader().Hash() != genesis.Hash() {
+			t.Errorf("last header hash mismatch: have: %x, want %x", ncm.CurrentHeader().Hash(), genesis.Hash())
 		}
 	}
 }
 
-func TestInsertNonceError(t *testing.T) {
+// Tests chain insertions in the face of one entity containing an invalid nonce.
+func TestHeadersInsertNonceError(t *testing.T) { testInsertNonceError(t, false) }
+func TestBlocksInsertNonceError(t *testing.T)  { testInsertNonceError(t, true) }
+
+func testInsertNonceError(t *testing.T, full bool) {
 	for i := 1; i < 25 && !t.Failed(); i++ {
-		db, _ := ethdb.NewMemDatabase()
-		genesis, err := WriteTestNetGenesisBlock(db, 0)
+		// Create a pristine chain and database
+		db, processor, err := newCanonical(0, full)
 		if err != nil {
-			t.Error(err)
-			t.FailNow()
+			t.Fatalf("failed to create pristine chain: %v", err)
 		}
-		bc := chm(genesis, db)
-		bc.processor = NewBlockProcessor(db, bc.pow, bc, bc.eventMux)
-		blocks := makeChain(bc.currentBlock, i, db, 0)
+		bc := processor.bc
+
+		// Create and insert a chain with a failing nonce
+		var (
+			failAt   int
+			failRes  int
+			failNum  uint64
+			failHash common.Hash
+		)
+		if full {
+			blocks := makeBlockChain(processor.bc.CurrentBlock(), i, db, 0)
+
+			failAt = rand.Int() % len(blocks)
+			failNum = blocks[failAt].NumberU64()
+			failHash = blocks[failAt].Hash()
+
+			processor.bc.pow = failPow{failNum}
+			failRes, err = processor.bc.InsertChain(blocks)
+		} else {
+			headers := makeHeaderChain(processor.bc.CurrentHeader(), i, db, 0)
 
-		fail := rand.Int() % len(blocks)
-		failblock := blocks[fail]
-		bc.pow = failPow{failblock.NumberU64()}
-		n, err := bc.InsertChain(blocks)
+			failAt = rand.Int() % len(headers)
+			failNum = headers[failAt].Number.Uint64()
+			failHash = headers[failAt].Hash()
 
+			processor.bc.pow = failPow{failNum}
+			failRes, err = processor.bc.InsertHeaderChain(headers, true)
+		}
 		// Check that the returned error indicates the nonce failure.
-		if n != fail {
-			t.Errorf("(i=%d) wrong failed block index: got %d, want %d", i, n, fail)
+		if failRes != failAt {
+			t.Errorf("test %d: failure index mismatch: have %d, want %d", i, failRes, failAt)
 		}
 		if !IsBlockNonceErr(err) {
-			t.Fatalf("(i=%d) got %q, want a nonce error", i, err)
+			t.Fatalf("test %d: error mismatch: have %v, want nonce error", i, err)
 		}
 		nerr := err.(*BlockNonceErr)
-		if nerr.Number.Cmp(failblock.Number()) != 0 {
-			t.Errorf("(i=%d) wrong block number in error, got %v, want %v", i, nerr.Number, failblock.Number())
+		if nerr.Number.Uint64() != failNum {
+			t.Errorf("test %d: number mismatch: have %v, want %v", i, nerr.Number, failNum)
 		}
-		if nerr.Hash != failblock.Hash() {
-			t.Errorf("(i=%d) wrong block hash in error, got %v, want %v", i, nerr.Hash, failblock.Hash())
+		if nerr.Hash != failHash {
+			t.Errorf("test %d: hash mismatch: have %x, want %x", i, nerr.Hash[:4], failHash[:4])
 		}
-
 		// Check that all no blocks after the failing block have been inserted.
-		for _, block := range blocks[fail:] {
-			if bc.HasBlock(block.Hash()) {
-				t.Errorf("(i=%d) invalid block %d present in chain", i, block.NumberU64())
+		for j := 0; j < i-failAt; j++ {
+			if full {
+				if block := bc.GetBlockByNumber(failNum + uint64(j)); block != nil {
+					t.Errorf("test %d: invalid block in chain: %v", i, block)
+				}
+			} else {
+				if header := bc.GetHeaderByNumber(failNum + uint64(j)); header != nil {
+					t.Errorf("test %d: invalid header in chain: %v", i, header)
+				}
 			}
 		}
 	}
diff --git a/core/chain_makers.go b/core/chain_makers.go
index 85a4955db..eb451c00d 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -211,25 +211,49 @@ func makeHeader(parent *types.Block, state *state.StateDB) *types.Header {
 	}
 }
 
-// newCanonical creates a new deterministic canonical chain by running
-// InsertChain on the result of makeChain.
-func newCanonical(n int, db ethdb.Database) (*BlockProcessor, error) {
+// newCanonical creates a chain database, and injects a deterministic canonical
+// chain. Depending on the full flag, if creates either a full block chain or a
+// header only chain.
+func newCanonical(n int, full bool) (ethdb.Database, *BlockProcessor, error) {
+	// Create te new chain database
+	db, _ := ethdb.NewMemDatabase()
 	evmux := &event.TypeMux{}
 
-	WriteTestNetGenesisBlock(db, 0)
-	chainman, _ := NewBlockChain(db, FakePow{}, evmux)
-	bman := NewBlockProcessor(db, FakePow{}, chainman, evmux)
-	bman.bc.SetProcessor(bman)
-	parent := bman.bc.CurrentBlock()
+	// Initialize a fresh chain with only a genesis block
+	genesis, _ := WriteTestNetGenesisBlock(db, 0)
+
+	blockchain, _ := NewBlockChain(db, FakePow{}, evmux)
+	processor := NewBlockProcessor(db, FakePow{}, blockchain, evmux)
+	processor.bc.SetProcessor(processor)
+
+	// Create and inject the requested chain
 	if n == 0 {
-		return bman, nil
+		return db, processor, nil
+	}
+	if full {
+		// Full block-chain requested
+		blocks := makeBlockChain(genesis, n, db, canonicalSeed)
+		_, err := blockchain.InsertChain(blocks)
+		return db, processor, err
+	}
+	// Header-only chain requested
+	headers := makeHeaderChain(genesis.Header(), n, db, canonicalSeed)
+	_, err := blockchain.InsertHeaderChain(headers, true)
+	return db, processor, err
+}
+
+// makeHeaderChain creates a deterministic chain of headers rooted at parent.
+func makeHeaderChain(parent *types.Header, n int, db ethdb.Database, seed int) []*types.Header {
+	blocks := makeBlockChain(types.NewBlockWithHeader(parent), n, db, seed)
+	headers := make([]*types.Header, len(blocks))
+	for i, block := range blocks {
+		headers[i] = block.Header()
 	}
-	lchain := makeChain(parent, n, db, canonicalSeed)
-	_, err := bman.bc.InsertChain(lchain)
-	return bman, err
+	return headers
 }
 
-func makeChain(parent *types.Block, n int, db ethdb.Database, seed int) []*types.Block {
+// makeBlockChain creates a deterministic chain of blocks rooted at parent.
+func makeBlockChain(parent *types.Block, n int, db ethdb.Database, seed int) []*types.Block {
 	return GenerateChain(parent, db, n, func(i int, b *BlockGen) {
 		b.SetCoinbase(common.Address{0: byte(seed), 19: byte(i)})
 	})
diff --git a/core/types/block.go b/core/types/block.go
index 7a84045a6..f7baa2175 100644
--- a/core/types/block.go
+++ b/core/types/block.go
@@ -184,7 +184,7 @@ var (
 // are ignored and set to values derived from the given txs, uncles
 // and receipts.
 func NewBlock(header *Header, txs []*Transaction, uncles []*Header, receipts []*Receipt) *Block {
-	b := &Block{header: copyHeader(header), td: new(big.Int)}
+	b := &Block{header: CopyHeader(header), td: new(big.Int)}
 
 	// TODO: panic if len(txs) != len(receipts)
 	if len(txs) == 0 {
@@ -210,7 +210,7 @@ func NewBlock(header *Header, txs []*Transaction, uncles []*Header, receipts []*
 		b.header.UncleHash = CalcUncleHash(uncles)
 		b.uncles = make([]*Header, len(uncles))
 		for i := range uncles {
-			b.uncles[i] = copyHeader(uncles[i])
+			b.uncles[i] = CopyHeader(uncles[i])
 		}
 	}
 
@@ -221,10 +221,12 @@ func NewBlock(header *Header, txs []*Transaction, uncles []*Header, receipts []*
 // header data is copied, changes to header and to the field values
 // will not affect the block.
 func NewBlockWithHeader(header *Header) *Block {
-	return &Block{header: copyHeader(header)}
+	return &Block{header: CopyHeader(header)}
 }
 
-func copyHeader(h *Header) *Header {
+// CopyHeader creates a deep copy of a block header to prevent side effects from
+// modifying a header variable.
+func CopyHeader(h *Header) *Header {
 	cpy := *h
 	if cpy.Time = new(big.Int); h.Time != nil {
 		cpy.Time.Set(h.Time)
@@ -326,7 +328,7 @@ func (b *Block) ReceiptHash() common.Hash { return b.header.ReceiptHash }
 func (b *Block) UncleHash() common.Hash   { return b.header.UncleHash }
 func (b *Block) Extra() []byte            { return common.CopyBytes(b.header.Extra) }
 
-func (b *Block) Header() *Header { return copyHeader(b.header) }
+func (b *Block) Header() *Header { return CopyHeader(b.header) }
 
 func (b *Block) HashNoNonce() common.Hash {
 	return b.header.HashNoNonce()
@@ -370,13 +372,13 @@ func (b *Block) WithMiningResult(nonce uint64, mixDigest common.Hash) *Block {
 // WithBody returns a new block with the given transaction and uncle contents.
 func (b *Block) WithBody(transactions []*Transaction, uncles []*Header) *Block {
 	block := &Block{
-		header:       copyHeader(b.header),
+		header:       CopyHeader(b.header),
 		transactions: make([]*Transaction, len(transactions)),
 		uncles:       make([]*Header, len(uncles)),
 	}
 	copy(block.transactions, transactions)
 	for i := range uncles {
-		block.uncles[i] = copyHeader(uncles[i])
+		block.uncles[i] = CopyHeader(uncles[i])
 	}
 	return block
 }