accounts/abi/backends: change SimulatedBackend to interface

accounts/abi/bind/backends/simulated.go

@@ -19,8 +19,12 @@ package backends
 import (
 	"context"
 	"math"
+	"math/big"
+	"time"
 
+	"github.com/ethereum/go-ethereum"
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
+	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/eth"
 	"github.com/ethereum/go-ethereum/eth/catalyst"
@@ -34,9 +38,51 @@ import (
 	"github.com/ethereum/go-ethereum/rpc"
 )
 
-var _ bind.ContractBackend = (*SimulatedBackend)(nil)
+var _ bind.ContractBackend = (*simBackend)(nil)
 
-type SimulatedBackend struct {
+type SimChainManagement interface {
+	// Commit seals a block and moves the chain forward to a new empty block.
+	Commit() common.Hash
+
+	// Rollback un-sends previously added transactions.
+	Rollback()
+
+	// Fork sets the head to a new block, which is based on the provided parentHash.
+	Fork(ctx context.Context, parentHash common.Hash) error
+
+	// AdjustTime changes the block timestamp.
+	AdjustTime(adjustment time.Duration) error
+
+	// Close closes the backend. You need to call this to clean up resources.
+	Close() error
+}
+
+// TODO: these methods should have their own interface in the ethereum package.
+type SimChainExtras interface {
+	BlockNumber(context.Context) (uint64, error)
+	ChainID(context.Context) (*big.Int, error)
+}
+
+// SimulatedBackend all interfaces in the ethereum package, but is based on a
+// simulated blockchain. It is intended for testing purposes.
+type SimulatedBackend interface {
+	SimChainManagement
+
+	// The backend implements all interfaces in the ethereum package.
+	ethereum.ChainReader
+	ethereum.ChainStateReader
+	ethereum.ContractCaller
+	ethereum.GasEstimator
+	ethereum.LogFilterer
+	ethereum.GasPricer
+	ethereum.PendingStateReader
+	ethereum.PendingContractCaller
+	ethereum.TransactionReader
+	ethereum.TransactionSender
+	SimChainExtras
+}
+
+type simBackend struct {
 	eth *eth.Ethereum
 	*catalyst.SimulatedBeacon
 	*ethclient.Client
@@ -45,7 +91,7 @@ type SimulatedBackend struct {
 // NewSimulatedBackend creates a new binding backend using a simulated blockchain
 // for testing purposes.
 // A simulated backend always uses chainID 1337.
-func NewSimulatedBackend(alloc core.GenesisAlloc, gasLimit uint64) *SimulatedBackend {
+func NewSimulatedBackend(alloc core.GenesisAlloc, gasLimit uint64) SimulatedBackend {
 	// Setup the node object
 	nodeConf := node.DefaultConfig
 	nodeConf.DataDir = ""
@@ -76,7 +122,7 @@ func NewSimulatedBackend(alloc core.GenesisAlloc, gasLimit uint64) *SimulatedBac
 // NewSimWithNode sets up a simulated backend on an existing node
 // this allows users to do persistent simulations.
 // The provided node must not be started and will be started by NewSimWithNode
-func NewSimWithNode(stack *node.Node, conf *eth.Config, blockPeriod uint64) (*SimulatedBackend, error) {
+func NewSimWithNode(stack *node.Node, conf *eth.Config, blockPeriod uint64) (SimulatedBackend, error) {
 	backend, err := eth.New(stack, conf)
 	if err != nil {
 		return nil, err
@@ -105,14 +151,14 @@ func NewSimWithNode(stack *node.Node, conf *eth.Config, blockPeriod uint64) (*Si
 		return nil, err
 	}
 
-	return &SimulatedBackend{
+	return &simBackend{
 		eth:             backend,
 		SimulatedBeacon: beacon,
 		Client:          ethclient.NewClient(stack.Attach()),
 	}, nil
 }
 
-func (n *SimulatedBackend) Close() error {
+func (n *simBackend) Close() error {
 	if n.Client != nil {
 		n.Client.Close()
 		n.Client = nil

accounts/abi/bind/backends/simulated_test.go

@@ -36,7 +36,7 @@ var (
 	testAddr   = crypto.PubkeyToAddress(testKey.PublicKey)
 )
 
-func simTestBackend(testAddr common.Address) *SimulatedBackend {
+func simTestBackend(testAddr common.Address) SimulatedBackend {
 	return NewSimulatedBackend(
 		core.GenesisAlloc{
 			testAddr: {Balance: big.NewInt(10000000000000000)},
@@ -44,12 +44,7 @@ func simTestBackend(testAddr common.Address) *SimulatedBackend {
 	)
 }
 
-func (sim *SimulatedBackend) currentBlock() *types.Block {
-	current, _ := sim.BlockByNumber(context.Background(), nil)
-	return current
-}
-
-func (sim *SimulatedBackend) newTx(key *ecdsa.PrivateKey) (*types.Transaction, error) {
+func newTx(sim SimulatedBackend, key *ecdsa.PrivateKey) (*types.Transaction, error) {
 	// create a signed transaction to send
 	head, _ := sim.HeaderByNumber(context.Background(), nil) // Should be child's, good enough
 	gasPrice := new(big.Int).Add(head.BaseFee, big.NewInt(1))
@@ -113,7 +108,7 @@ func TestSendTransaction(t *testing.T) {
 	defer sim.Close()
 	bgCtx := context.Background()
 
-	signedTx, err := sim.newTx(testKey)
+	signedTx, err := newTx(sim, testKey)
 	if err != nil {
 		t.Errorf("could not create transaction: %v", err)
 	}
@@ -148,25 +143,35 @@ func TestFork(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 	sim := simTestBackend(testAddr)
 	defer sim.Close()
+
+	ctx := context.Background()
+
 	// 1.
-	parent := sim.currentBlock()
+	parent, _ := sim.HeaderByNumber(ctx, nil)
+
 	// 2.
 	n := int(rand.Int31n(21))
 	for i := 0; i < n; i++ {
 		sim.Commit()
 	}
+
 	// 3.
-	if sim.currentBlock().Number().Uint64() != uint64(n) {
+	b, _ := sim.BlockNumber(ctx)
+	if b != uint64(n) {
 		t.Error("wrong chain length")
 	}
+
 	// 4.
-	sim.Fork(context.Background(), parent.Hash())
+	sim.Fork(ctx, parent.Hash())
+
 	// 5.
 	for i := 0; i < n+1; i++ {
 		sim.Commit()
 	}
+
 	// 6.
-	if sim.currentBlock().Number().Uint64() != uint64(n+1) {
+	b, _ = sim.BlockNumber(ctx)
+	if b != uint64(n+1) {
 		t.Error("wrong chain length")
 	}
 }
@@ -185,24 +190,30 @@ func TestForkResendTx(t *testing.T) {
 	testAddr := crypto.PubkeyToAddress(testKey.PublicKey)
 	sim := simTestBackend(testAddr)
 	defer sim.Close()
+
 	// 1.
-	parent := sim.currentBlock()
+	ctx := context.Background()
+	parent, _ := sim.HeaderByNumber(ctx, nil)
+
 	// 2.
-	tx, err := sim.newTx(testKey)
+	tx, err := newTx(sim, testKey)
 	if err != nil {
 		t.Fatalf("could not create transaction: %v", err)
 	}
 	sim.SendTransaction(context.Background(), tx)
 	sim.Commit()
+
 	// 3.
 	receipt, _ := sim.TransactionReceipt(context.Background(), tx.Hash())
 	if h := receipt.BlockNumber.Uint64(); h != 1 {
 		t.Errorf("TX included in wrong block: %d", h)
 	}
+
 	// 4.
 	if err := sim.Fork(context.Background(), parent.Hash()); err != nil {
 		t.Errorf("forking: %v", err)
 	}
+
 	// 5.
 	sim.Commit()
 	if err := sim.SendTransaction(context.Background(), tx); err != nil {
@@ -223,7 +234,8 @@ func TestCommitReturnValue(t *testing.T) {
 
 	// Test if Commit returns the correct block hash
 	h1 := sim.Commit()
-	if h1 != sim.currentBlock().Hash() {
+	cur, _ := sim.HeaderByNumber(context.Background(), nil)
+	if h1 != cur.Hash() {
 		t.Error("Commit did not return the hash of the last block.")
 	}
 
@@ -262,14 +274,15 @@ func TestAdjustTimeAfterFork(t *testing.T) {
 	defer sim.Close()
 
 	sim.Commit() // h1
-	h1 := sim.currentBlock().Hash()
+	h1, _ := sim.HeaderByNumber(context.Background(), nil)
+
 	sim.Commit() // h2
-	sim.Fork(context.Background(), h1)
+	sim.Fork(context.Background(), h1.Hash())
 	sim.AdjustTime(1 * time.Second)
 	sim.Commit()
 
-	head := sim.currentBlock()
-	if head.Number() == common.Big2 && head.ParentHash() != h1 {
+	head, _ := sim.HeaderByNumber(context.Background(), nil)
+	if head.Number.Uint64() == 2 && head.ParentHash != h1.Hash() {
 		t.Errorf("failed to build block on fork")
 	}
 }