Merge branch 'develop' into feat/reduce-executor-size

op-e2e/actions/l2_engine_test.go

@@ -191,7 +191,7 @@ func TestL2EngineAPIFail(gt *testing.T) {
 }
 
 func TestEngineAPITests(t *testing.T) {
-	test.RunEngineAPITests(t, func() engineapi.EngineBackend {
+	test.RunEngineAPITests(t, func(t *testing.T) engineapi.EngineBackend {
 		jwtPath := e2eutils.WriteDefaultJWT(t)
 		dp := e2eutils.MakeDeployParams(t, defaultRollupTestParams)
 		sd := e2eutils.Setup(t, dp, defaultAlloc)

op-e2e/system_test.go

@@ -589,8 +589,10 @@ func TestSystemMockP2P(t *testing.T) {
 	}
 
 	cfg := DefaultSystemConfig(t)
-	// Disable batcher, so we don't sync from L1
+	// Disable batcher, so we don't sync from L1 & set a large sequence window so we only have unsafe blocks
 	cfg.DisableBatcher = true
+	cfg.DeployConfig.SequencerWindowSize = 100_000
+	cfg.DeployConfig.MaxSequencerDrift = 100_000
 	// disable at the start, so we don't miss any gossiped blocks.
 	cfg.Nodes["sequencer"].Driver.SequencerStopped = true
 

op-node/sources/batching.go

@@ -24,7 +24,6 @@ type IterativeBatchCall[K any, V any] struct {
 
 	makeRequest func(K) (V, rpc.BatchElem)
 	getBatch    BatchCallContextFn
-	getSingle   CallContextFn
 
 	requestsValues []V
 	scheduled      chan rpc.BatchElem
@@ -36,7 +35,6 @@ func NewIterativeBatchCall[K any, V any](
 	requestsKeys []K,
 	makeRequest func(K) (V, rpc.BatchElem),
 	getBatch BatchCallContextFn,
-	getSingle CallContextFn,
 	batchSize int) *IterativeBatchCall[K, V] {
 
 	if len(requestsKeys) < batchSize {
@@ -49,7 +47,6 @@ func NewIterativeBatchCall[K any, V any](
 	out := &IterativeBatchCall[K, V]{
 		completed:    0,
 		getBatch:     getBatch,
-		getSingle:    getSingle,
 		requestsKeys: requestsKeys,
 		batchSize:    batchSize,
 		makeRequest:  makeRequest,
@@ -122,23 +119,11 @@ func (ibc *IterativeBatchCall[K, V]) Fetch(ctx context.Context) error {
 		break
 	}
 
-	if len(batch) == 0 {
-		return nil
-	}
-
-	if ibc.batchSize == 1 {
-		first := batch[0]
-		if err := ibc.getSingle(ctx, &first.Result, first.Method, first.Args...); err != nil {
-			ibc.scheduled <- first
-			return err
-		}
-	} else {
-		if err := ibc.getBatch(ctx, batch); err != nil {
-			for _, r := range batch {
-				ibc.scheduled <- r
-			}
-			return fmt.Errorf("failed batch-retrieval: %w", err)
+	if err := ibc.getBatch(ctx, batch); err != nil {
+		for _, r := range batch {
+			ibc.scheduled <- r
 		}
+		return fmt.Errorf("failed batch-retrieval: %w", err)
 	}
 	var result error
 	for _, elem := range batch {

op-node/sources/batching_test.go

@@ -34,8 +34,7 @@ type batchTestCase struct {
 
 	batchSize int
 
-	batchCalls  []batchCall
-	singleCalls []elemCall
+	batchCalls []batchCall
 
 	mock.Mock
 }
@@ -54,14 +53,7 @@ func (tc *batchTestCase) GetBatch(ctx context.Context, b []rpc.BatchElem) error
 	if ctx.Err() != nil {
 		return ctx.Err()
 	}
-	return tc.Mock.MethodCalled("getBatch", b).Get(0).([]error)[0]
-}
-
-func (tc *batchTestCase) GetSingle(ctx context.Context, result any, method string, args ...any) error {
-	if ctx.Err() != nil {
-		return ctx.Err()
-	}
-	return tc.Mock.MethodCalled("getSingle", (*(result.(*interface{}))).(*string), method, args[0]).Get(0).([]error)[0]
+	return tc.Mock.MethodCalled("get", b).Get(0).([]error)[0]
 }
 
 var mockErr = errors.New("mockErr")
@@ -72,7 +64,7 @@ func (tc *batchTestCase) Run(t *testing.T) {
 		keys[i] = i
 	}
 
-	makeBatchMock := func(bci int, bc batchCall) func(args mock.Arguments) {
+	makeMock := func(bci int, bc batchCall) func(args mock.Arguments) {
 		return func(args mock.Arguments) {
 			batch := args[0].([]rpc.BatchElem)
 			for i, elem := range batch {
@@ -102,30 +94,10 @@ func (tc *batchTestCase) Run(t *testing.T) {
 			})
 		}
 		if len(bc.elems) > 0 {
-			tc.On("getBatch", batch).Once().Run(makeBatchMock(bci, bc)).Return([]error{bc.rpcErr}) // wrap to preserve nil as type of error
-		}
-	}
-	makeSingleMock := func(eci int, ec elemCall) func(args mock.Arguments) {
-		return func(args mock.Arguments) {
-			result := args[0].(*string)
-			id := args[2].(int)
-			require.Equal(t, ec.id, id, "element should match expected element")
-			if ec.err {
-				*result = ""
-			} else {
-				*result = fmt.Sprintf("mock result id %d", id)
-			}
+			tc.On("get", batch).Once().Run(makeMock(bci, bc)).Return([]error{bc.rpcErr}) // wrap to preserve nil as type of error
 		}
 	}
-	// mock the results of unbatched calls
-	for eci, ec := range tc.singleCalls {
-		var ret error
-		if ec.err {
-			ret = mockErr
-		}
-		tc.On("getSingle", new(string), "testing_foobar", ec.id).Once().Run(makeSingleMock(eci, ec)).Return([]error{ret})
-	}
-	iter := NewIterativeBatchCall[int, *string](keys, makeTestRequest, tc.GetBatch, tc.GetSingle, tc.batchSize)
+	iter := NewIterativeBatchCall[int, *string](keys, makeTestRequest, tc.GetBatch, tc.batchSize)
 	for i, bc := range tc.batchCalls {
 		ctx := context.Background()
 		if bc.makeCtx != nil {
@@ -144,20 +116,6 @@ func (tc *batchTestCase) Run(t *testing.T) {
 			}
 		}
 	}
-	for i, ec := range tc.singleCalls {
-		ctx := context.Background()
-		err := iter.Fetch(ctx)
-		if err == io.EOF {
-			require.Equal(t, i, len(tc.singleCalls)-1, "EOF only on last call")
-		} else {
-			require.False(t, iter.Complete())
-			if ec.err {
-				require.Error(t, err)
-			} else {
-				require.NoError(t, err)
-			}
-		}
-	}
 	require.True(t, iter.Complete(), "batch iter should be complete after the expected calls")
 	out, err := iter.Result()
 	require.NoError(t, err)
@@ -196,37 +154,6 @@ func TestFetchBatched(t *testing.T) {
 				},
 			},
 		},
-		{
-			name:      "single element",
-			items:     1,
-			batchSize: 4,
-			singleCalls: []elemCall{
-				{id: 0, err: false},
-			},
-		},
-		{
-			name:      "unbatched",
-			items:     4,
-			batchSize: 1,
-			singleCalls: []elemCall{
-				{id: 0, err: false},
-				{id: 1, err: false},
-				{id: 2, err: false},
-				{id: 3, err: false},
-			},
-		},
-		{
-			name:      "unbatched with retry",
-			items:     4,
-			batchSize: 1,
-			singleCalls: []elemCall{
-				{id: 0, err: false},
-				{id: 1, err: true},
-				{id: 2, err: false},
-				{id: 3, err: false},
-				{id: 1, err: false},
-			},
-		},
 		{
 			name:      "split",
 			items:     5,
@@ -313,7 +240,7 @@ func TestFetchBatched(t *testing.T) {
 		},
 		{
 			name:      "context timeout",
-			items:     2,
+			items:     1,
 			batchSize: 3,
 			batchCalls: []batchCall{
 				{
@@ -328,7 +255,6 @@ func TestFetchBatched(t *testing.T) {
 				{
 					elems: []elemCall{
 						{id: 0, err: false},
-						{id: 1, err: false},
 					},
 					err: "",
 				},

op-node/sources/receipts.go

@@ -373,7 +373,6 @@ func (job *receiptsFetchingJob) runFetcher(ctx context.Context) error {
 			job.txHashes,
 			makeReceiptRequest,
 			job.client.BatchCallContext,
-			job.client.CallContext,
 			job.maxBatchSize,
 		)
 	}

op-program/client/l2/engine_backend.go

@@ -18,14 +18,15 @@ import (
 )
 
 type OracleBackedL2Chain struct {
-	log       log.Logger
-	oracle    Oracle
-	chainCfg  *params.ChainConfig
-	engine    consensus.Engine
-	head      *types.Header
-	safe      *types.Header
-	finalized *types.Header
-	vmCfg     vm.Config
+	log        log.Logger
+	oracle     Oracle
+	chainCfg   *params.ChainConfig
+	engine     consensus.Engine
+	oracleHead *types.Header
+	head       *types.Header
+	safe       *types.Header
+	finalized  *types.Header
+	vmCfg      vm.Config
 
 	// Inserted blocks
 	blocks map[common.Hash]*types.Block
@@ -44,11 +45,12 @@ func NewOracleBackedL2Chain(logger log.Logger, oracle Oracle, chainCfg *params.C
 		engine:   beacon.New(nil),
 
 		// Treat the agreed starting head as finalized - nothing before it can be disputed
-		head:      head.Header(),
-		safe:      head.Header(),
-		finalized: head.Header(),
-		blocks:    make(map[common.Hash]*types.Block),
-		db:        NewOracleBackedDB(oracle),
+		head:       head.Header(),
+		safe:       head.Header(),
+		finalized:  head.Header(),
+		oracleHead: head.Header(),
+		blocks:     make(map[common.Hash]*types.Block),
+		db:         NewOracleBackedDB(oracle),
 	}, nil
 }
 
@@ -82,11 +84,7 @@ func (o *OracleBackedL2Chain) CurrentFinalBlock() *types.Header {
 }
 
 func (o *OracleBackedL2Chain) GetHeaderByHash(hash common.Hash) *types.Header {
-	block := o.GetBlockByHash(hash)
-	if block == nil {
-		return nil
-	}
-	return block.Header()
+	return o.GetBlockByHash(hash).Header()
 }
 
 func (o *OracleBackedL2Chain) GetBlockByHash(hash common.Hash) *types.Block {
@@ -96,15 +94,18 @@ func (o *OracleBackedL2Chain) GetBlockByHash(hash common.Hash) *types.Block {
 		return block
 	}
 	// Retrieve from the oracle
-	block = o.oracle.BlockByHash(hash)
-	if block == nil {
-		return nil
-	}
-	return block
+	return o.oracle.BlockByHash(hash)
 }
 
 func (o *OracleBackedL2Chain) GetBlock(hash common.Hash, number uint64) *types.Block {
-	block := o.GetBlockByHash(hash)
+	var block *types.Block
+	if o.oracleHead.Number.Uint64() < number {
+		// For blocks above the chain head, only consider newly built blocks
+		// Avoids requesting an unknown block from the oracle which would panic.
+		block = o.blocks[hash]
+	} else {
+		block = o.GetBlockByHash(hash)
+	}
 	if block == nil {
 		return nil
 	}
@@ -116,9 +117,6 @@ func (o *OracleBackedL2Chain) GetBlock(hash common.Hash, number uint64) *types.B
 
 func (o *OracleBackedL2Chain) GetHeader(hash common.Hash, u uint64) *types.Header {
 	block := o.GetBlock(hash, u)
-	if block == nil {
-		return nil
-	}
 	return block.Header()
 }
 

op-program/client/l2/engine_backend_test.go

@@ -42,17 +42,6 @@ func TestGetBlocks(t *testing.T) {
 	}
 }
 
-func TestUnknownBlock(t *testing.T) {
-	_, chain := setupOracleBackedChain(t, 1)
-	hash := common.HexToHash("0x556677881122")
-	blockNumber := uint64(1)
-	require.Nil(t, chain.GetBlockByHash(hash))
-	require.Nil(t, chain.GetHeaderByHash(hash))
-	require.Nil(t, chain.GetBlock(hash, blockNumber))
-	require.Nil(t, chain.GetHeader(hash, blockNumber))
-	require.False(t, chain.HasBlockAndState(hash, blockNumber))
-}
-
 func TestCanonicalHashNotFoundPastChainHead(t *testing.T) {
 	blocks, chain := setupOracleBackedChainWithLowerHead(t, 5, 3)
 
@@ -69,7 +58,7 @@ func TestCanonicalHashNotFoundPastChainHead(t *testing.T) {
 func TestAppendToChain(t *testing.T) {
 	blocks, chain := setupOracleBackedChainWithLowerHead(t, 4, 3)
 	newBlock := blocks[4]
-	require.Nil(t, chain.GetBlockByHash(newBlock.Hash()), "block unknown before being added")
+	require.Nil(t, chain.GetBlock(newBlock.Hash(), newBlock.NumberU64()), "block unknown before being added")
 
 	require.NoError(t, chain.InsertBlockWithoutSetHead(newBlock))
 	require.Equal(t, blocks[3].Header(), chain.CurrentHeader(), "should not update chain head yet")
@@ -113,9 +102,7 @@ func TestUpdateStateDatabaseWhenImportingBlock(t *testing.T) {
 
 	require.NotEqual(t, blocks[1].Root(), newBlock.Root(), "block should have modified world state")
 
-	require.Panics(t, func() {
-		_, _ = chain.StateAt(newBlock.Root())
-	}, "state from non-imported block should not be available")
+	require.False(t, chain.HasBlockAndState(newBlock.Root(), newBlock.NumberU64()), "state from non-imported block should not be available")
 
 	err = chain.InsertBlockWithoutSetHead(newBlock)
 	require.NoError(t, err)
@@ -181,7 +168,7 @@ func setupOracle(t *testing.T, blockCount int, headBlockNumber int) (*params.Cha
 	genesisBlock := l2Genesis.MustCommit(db)
 	blocks, _ := core.GenerateChain(chainCfg, genesisBlock, consensus, db, blockCount, func(i int, gen *core.BlockGen) {})
 	blocks = append([]*types.Block{genesisBlock}, blocks...)
-	oracle := newStubBlockOracle(blocks[:headBlockNumber+1], db)
+	oracle := newStubBlockOracle(t, blocks[:headBlockNumber+1], db)
 	return chainCfg, blocks, oracle
 }
 
@@ -213,23 +200,27 @@ type stubBlockOracle struct {
 	kvStateOracle
 }
 
-func newStubBlockOracle(chain []*types.Block, db ethdb.Database) *stubBlockOracle {
+func newStubBlockOracle(t *testing.T, chain []*types.Block, db ethdb.Database) *stubBlockOracle {
 	blocks := make(map[common.Hash]*types.Block, len(chain))
 	for _, block := range chain {
 		blocks[block.Hash()] = block
 	}
 	return &stubBlockOracle{
 		blocks:        blocks,
-		kvStateOracle: kvStateOracle{source: db},
+		kvStateOracle: kvStateOracle{t: t, source: db},
 	}
 }
 
 func (o stubBlockOracle) BlockByHash(blockHash common.Hash) *types.Block {
-	return o.blocks[blockHash]
+	block, ok := o.blocks[blockHash]
+	if !ok {
+		o.t.Fatalf("requested unknown block %s", blockHash)
+	}
+	return block
 }
 
 func TestEngineAPITests(t *testing.T) {
-	test.RunEngineAPITests(t, func() engineapi.EngineBackend {
+	test.RunEngineAPITests(t, func(t *testing.T) engineapi.EngineBackend {
 		_, chain := setupOracleBackedChain(t, 0)
 		return chain
 	})

op-program/client/l2/engineapi/l2_engine_api.go

@@ -301,7 +301,7 @@ func (ea *L2EngineAPI) NewPayloadV1(ctx context.Context, payload *eth.ExecutionP
 	}
 	// If we already have the block locally, ignore the entire execution and just
 	// return a fake success.
-	if block := ea.backend.GetBlockByHash(payload.BlockHash); block != nil {
+	if block := ea.backend.GetBlock(payload.BlockHash, uint64(payload.BlockNumber)); block != nil {
 		ea.log.Warn("Ignoring already known beacon payload", "number", payload.BlockNumber, "hash", payload.BlockHash, "age", common.PrettyAge(time.Unix(int64(block.Time()), 0)))
 		hash := block.Hash()
 		return &eth.PayloadStatusV1{Status: eth.ExecutionValid, LatestValidHash: &hash}, nil

op-program/client/l2/engineapi/test/l2_engine_api_tests.go

@@ -18,7 +18,7 @@ import (
 var gasLimit = eth.Uint64Quantity(30_000_000)
 var feeRecipient = common.Address{}
 
-func RunEngineAPITests(t *testing.T, createBackend func() engineapi.EngineBackend) {
+func RunEngineAPITests(t *testing.T, createBackend func(t *testing.T) engineapi.EngineBackend) {
 	t.Run("CreateBlock", func(t *testing.T) {
 		api := newTestHelper(t, createBackend)
 
@@ -292,10 +292,10 @@ type testHelper struct {
 	assert  *require.Assertions
 }
 
-func newTestHelper(t *testing.T, createBackend func() engineapi.EngineBackend) *testHelper {
+func newTestHelper(t *testing.T, createBackend func(t *testing.T) engineapi.EngineBackend) *testHelper {
 	logger := testlog.Logger(t, log.LvlDebug)
 	ctx := context.Background()
-	backend := createBackend()
+	backend := createBackend(t)
 	api := engineapi.NewL2EngineAPI(logger, backend)
 	test := &testHelper{
 		t:       t,

op-program/host/l2/fetcher.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 
+	"github.com/ethereum-optimism/optimism/op-node/eth"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/core/rawdb"
@@ -24,19 +25,25 @@ type CallContext interface {
 type FetchingL2Oracle struct {
 	ctx         context.Context
 	logger      log.Logger
+	head        eth.BlockInfo
 	blockSource BlockSource
 	callContext CallContext
 }
 
-func NewFetchingL2Oracle(ctx context.Context, logger log.Logger, l2Url string) (*FetchingL2Oracle, error) {
+func NewFetchingL2Oracle(ctx context.Context, logger log.Logger, l2Url string, l2Head common.Hash) (*FetchingL2Oracle, error) {
 	rpcClient, err := rpc.Dial(l2Url)
 	if err != nil {
 		return nil, err
 	}
 	ethClient := ethclient.NewClient(rpcClient)
+	head, err := ethClient.HeaderByHash(ctx, l2Head)
+	if err != nil {
+		return nil, fmt.Errorf("retrieve l2 head %v: %w", l2Head, err)
+	}
 	return &FetchingL2Oracle{
 		ctx:         ctx,
 		logger:      logger,
+		head:        eth.HeaderBlockInfo(head),
 		blockSource: ethClient,
 		callContext: rpcClient,
 	}, nil
@@ -78,5 +85,8 @@ func (o *FetchingL2Oracle) BlockByHash(blockHash common.Hash) *types.Block {
 	if err != nil {
 		panic(fmt.Errorf("fetch block %s: %w", blockHash.Hex(), err))
 	}
+	if block.NumberU64() > o.head.NumberU64() {
+		panic(fmt.Errorf("fetched block %v number %d above head block number %d", blockHash, block.NumberU64(), o.head.NumberU64()))
+	}
 	return block
 }

op-program/host/l2/fetcher_test.go

@@ -5,12 +5,14 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"math/big"
 	"math/rand"
 	"reflect"
 	"testing"
 
 	"github.com/ethereum-optimism/optimism/op-node/testutils"
 	cll2 "github.com/ethereum-optimism/optimism/op-program/client/l2"
+	"github.com/ethereum/go-ethereum/trie"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
@@ -23,35 +25,7 @@ import (
 // Require the fetching oracle to implement StateOracle
 var _ cll2.StateOracle = (*FetchingL2Oracle)(nil)
 
-type callContextRequest struct {
-	ctx    context.Context
-	method string
-	args   []interface{}
-}
-type stubCallContext struct {
-	nextResult any
-	nextErr    error
-	requests   []callContextRequest
-}
-
-func (c *stubCallContext) CallContext(ctx context.Context, result any, method string, args ...interface{}) error {
-	if result != nil && reflect.TypeOf(result).Kind() != reflect.Ptr {
-		return fmt.Errorf("call result parameter must be pointer or nil interface: %v", result)
-	}
-	c.requests = append(c.requests, callContextRequest{ctx: ctx, method: method, args: args})
-	if c.nextErr != nil {
-		return c.nextErr
-	}
-	res, err := json.Marshal(c.nextResult)
-	if err != nil {
-		return fmt.Errorf("json marshal: %w", err)
-	}
-	err = json.Unmarshal(res, result)
-	if err != nil {
-		return fmt.Errorf("json unmarshal: %w", err)
-	}
-	return nil
-}
+const headBlockNumber = 1000
 
 func TestNodeByHash(t *testing.T) {
 	rng := rand.New(rand.NewSource(1234))
@@ -152,31 +126,12 @@ func TestCodeByHash(t *testing.T) {
 	})
 }
 
-type blockRequest struct {
-	ctx       context.Context
-	blockHash common.Hash
-}
-
-type stubBlockSource struct {
-	requests   []blockRequest
-	nextErr    error
-	nextResult *types.Block
-}
-
-func (s *stubBlockSource) BlockByHash(ctx context.Context, blockHash common.Hash) (*types.Block, error) {
-	s.requests = append(s.requests, blockRequest{
-		ctx:       ctx,
-		blockHash: blockHash,
-	})
-	return s.nextResult, s.nextErr
-}
-
 func TestBlockByHash(t *testing.T) {
 	rng := rand.New(rand.NewSource(1234))
 	hash := testutils.RandomHash(rng)
 
 	t.Run("Success", func(t *testing.T) {
-		block, _ := testutils.RandomBlock(rng, 1)
+		block := blockWithNumber(rng, headBlockNumber-1)
 		stub := &stubBlockSource{nextResult: block}
 		fetcher := newFetcher(stub, nil)
 
@@ -194,7 +149,7 @@ func TestBlockByHash(t *testing.T) {
 	})
 
 	t.Run("RequestArgs", func(t *testing.T) {
-		stub := &stubBlockSource{}
+		stub := &stubBlockSource{nextResult: blockWithNumber(rng, 1)}
 		fetcher := newFetcher(stub, nil)
 
 		fetcher.BlockByHash(hash)
@@ -203,11 +158,86 @@ func TestBlockByHash(t *testing.T) {
 		req := stub.requests[0]
 		require.Equal(t, hash, req.blockHash)
 	})
+
+	t.Run("PanicWhenBlockAboveHeadRequested", func(t *testing.T) {
+		// Block that the source can provide but is above the head block number
+		block := blockWithNumber(rng, headBlockNumber+1)
+
+		stub := &stubBlockSource{nextResult: block}
+		fetcher := newFetcher(stub, nil)
+
+		require.Panics(t, func() {
+			fetcher.BlockByHash(block.Hash())
+		})
+	})
+}
+
+func blockWithNumber(rng *rand.Rand, num int64) *types.Block {
+	header := testutils.RandomHeader(rng)
+	header.Number = big.NewInt(num)
+	return types.NewBlock(header, nil, nil, nil, trie.NewStackTrie(nil))
+}
+
+type blockRequest struct {
+	ctx       context.Context
+	blockHash common.Hash
+}
+
+type stubBlockSource struct {
+	requests   []blockRequest
+	nextErr    error
+	nextResult *types.Block
+}
+
+func (s *stubBlockSource) BlockByHash(ctx context.Context, blockHash common.Hash) (*types.Block, error) {
+	s.requests = append(s.requests, blockRequest{
+		ctx:       ctx,
+		blockHash: blockHash,
+	})
+	return s.nextResult, s.nextErr
+}
+
+type callContextRequest struct {
+	ctx    context.Context
+	method string
+	args   []interface{}
+}
+
+type stubCallContext struct {
+	nextResult any
+	nextErr    error
+	requests   []callContextRequest
+}
+
+func (c *stubCallContext) CallContext(ctx context.Context, result any, method string, args ...interface{}) error {
+	if result != nil && reflect.TypeOf(result).Kind() != reflect.Ptr {
+		return fmt.Errorf("call result parameter must be pointer or nil interface: %v", result)
+	}
+	c.requests = append(c.requests, callContextRequest{ctx: ctx, method: method, args: args})
+	if c.nextErr != nil {
+		return c.nextErr
+	}
+	res, err := json.Marshal(c.nextResult)
+	if err != nil {
+		return fmt.Errorf("json marshal: %w", err)
+	}
+	err = json.Unmarshal(res, result)
+	if err != nil {
+		return fmt.Errorf("json unmarshal: %w", err)
+	}
+	return nil
 }
 
 func newFetcher(blockSource BlockSource, callContext CallContext) *FetchingL2Oracle {
+	rng := rand.New(rand.NewSource(int64(1)))
+	head := testutils.MakeBlockInfo(func(i *testutils.MockBlockInfo) {
+		i.InfoNum = headBlockNumber
+	})(rng)
+
 	return &FetchingL2Oracle{
+		ctx:         context.Background(),
 		logger:      log.New(),
+		head:        head,
 		blockSource: blockSource,
 		callContext: callContext,
 	}

op-program/host/l2/l2.go

@@ -19,7 +19,7 @@ func NewFetchingEngine(ctx context.Context, logger log.Logger, cfg *config.Confi
 	if err != nil {
 		return nil, err
 	}
-	oracle, err := NewFetchingL2Oracle(ctx, logger, cfg.L2URL)
+	oracle, err := NewFetchingL2Oracle(ctx, logger, cfg.L2URL, cfg.L2Head)
 	if err != nil {
 		return nil, fmt.Errorf("connect l2 oracle: %w", err)
 	}