diff --git a/consensus/system_contract/system_contract_test.go b/consensus/system_contract/system_contract_test.go
new file mode 100644
index 000000000000..36edf93aed93
--- /dev/null
+++ b/consensus/system_contract/system_contract_test.go
@@ -0,0 +1,250 @@
+package system_contract
+
+import (
+	"context"
+	"github.com/scroll-tech/go-ethereum"
+	"github.com/scroll-tech/go-ethereum/accounts"
+	"github.com/scroll-tech/go-ethereum/common"
+	"github.com/scroll-tech/go-ethereum/core/types"
+	"github.com/scroll-tech/go-ethereum/log"
+	"github.com/scroll-tech/go-ethereum/params"
+	"github.com/scroll-tech/go-ethereum/rollup/sync_service"
+	"github.com/scroll-tech/go-ethereum/trie"
+	"github.com/stretchr/testify/require"
+	"math/big"
+	"sync"
+	"testing"
+	"time"
+)
+
+var _ sync_service.EthClient = &fakeEthClient{}
+
+func TestSystemContract_FetchSigner(t *testing.T) {
+	// Turn off logging for tests to keep output clean.
+	log.Root().SetHandler(log.DiscardHandler())
+
+	// Expected signer address returned by our fake EthClient.
+	expectedSigner := common.HexToAddress("0x1234567890abcdef1234567890abcdef12345678")
+
+	// Create our fake client to always return expectedSigner.
+	fakeClient := &fakeEthClient{value: expectedSigner}
+
+	config := &params.SystemContractConfig{
+		SystemContractAddress: common.HexToAddress("0xFAKE"),
+		// The slot number can be arbitrary – fake client doesn't use it.
+		Period:        10,
+		RelaxedPeriod: false,
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	// Create a new SystemContract instance.
+	sys := New(ctx, config, fakeClient)
+	defer sys.Close()
+
+	// Since the SystemContract's Start() routine fetches and updates s.signerAddressL1
+	// in a separate goroutine, wait a bit for that to complete.
+	time.Sleep(2 * time.Second)
+
+	// Acquire a read lock to safely read the value.
+	sys.lock.RLock()
+	actualSigner := sys.signerAddressL1
+	sys.lock.RUnlock()
+
+	// Verify that the fetched signer equals the expectedSigner from our fake client.
+	require.Equal(t, expectedSigner, actualSigner, "The SystemContract should update signerAddressL1 to the value provided by the client")
+}
+
+func TestSystemContract_AuthorizeCheck(t *testing.T) {
+	// This test verifies that if the local signer does not match the authorized signer,
+	// then the Seal() function returns an error.
+
+	// Set the expected signer.
+	expectedSigner := common.HexToAddress("0x1234567890abcdef1234567890abcdef12345678")
+
+	fakeClient := &fakeEthClient{value: expectedSigner}
+	config := &params.SystemContractConfig{
+		SystemContractAddress: common.HexToAddress("0xFAKE"),
+		Period:                10,
+		RelaxedPeriod:         false,
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	sys := New(ctx, config, fakeClient)
+	defer sys.Close()
+
+	// Wait to ensure that the background routine has updated signerAddressL1.
+	time.Sleep(2 * time.Second)
+
+	// Authorize with a different signer than expected.
+	differentSigner := common.HexToAddress("0xABCDEFabcdefABCDEFabcdefabcdefABCDEFABCD")
+	sys.Authorize(differentSigner, func(acc accounts.Account, mimeType string, message []byte) ([]byte, error) {
+		// For testing, return a dummy signature
+		return []byte("dummy_sig"), nil
+	})
+
+	// Create a dummy block header (with dummy values).
+	// We only need the block number and extra data length for this test.
+	header := &types.Header{
+		Number: big.NewInt(100),
+		// We use an extra slice with length equal to extraSeal
+		Extra: make([]byte, extraSeal),
+		// Set other fields minimally for the test:
+		Time:       uint64(time.Now().Unix() + 10),
+		GasLimit:   10000000,
+		Nonce:      types.BlockNonce{}, // zero nonce as required
+		MixDigest:  common.Hash{},      // dummy; in a PoA system this should be zero
+		Difficulty: big.NewInt(1),
+	}
+
+	// Call Seal() and expect an error since local signer != authorized signer.
+	results := make(chan *types.Block)
+	stop := make(chan struct{})
+	err := sys.Seal(nil, (&types.Block{}).WithSeal(header), results, stop)
+
+	require.Error(t, err, "Seal should return an error when the local signer is not authorized")
+}
+
+// TestSystemContract_SignsAfterUpdate simulates:
+//  1. Initially, the SystemContract authorized signer (from StorageAt) is not the signer of the Block.
+//  2. Later, after updating the fake client to the correct signer, the background
+//     poll updates the SystemContract.
+//  3. Once updated, if the local signing key is set to match, Seal() should succeed.
+func TestSystemContract_SignsAfterUpdate(t *testing.T) {
+	// Silence logging during tests.
+	log.Root().SetHandler(log.DiscardHandler())
+
+	// Define two addresses: one "wrong" and one "correct".
+	oldSigner := common.HexToAddress("0x1111111111111111111111111111111111111111")
+	updatedSigner := common.HexToAddress("0x2222222222222222222222222222222222222222")
+
+	// Create a fake client that starts by returning the wrong signer.
+	fakeClient := &fakeEthClient{
+		value: oldSigner,
+	}
+
+	config := &params.SystemContractConfig{
+		SystemContractAddress: common.HexToAddress("0xFAKE"), // Dummy value
+		Period:                10,                            // arbitrary non-zero value
+		RelaxedPeriod:         false,
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
+	defer cancel()
+
+	// Create the SystemContract with our fake client.
+	sys := New(ctx, config, fakeClient)
+	defer sys.Close()
+
+	// Wait for the background routine to poll at least once.
+	time.Sleep(2 * time.Second)
+
+	// Verify that initially the fetched signer equals oldSigner.
+	sys.lock.RLock()
+	initialSigner := sys.signerAddressL1
+	sys.lock.RUnlock()
+	require.Equal(t, oldSigner, initialSigner, "Initial signerAddressL1 should be oldSigner")
+
+	// Now, simulate an update: change the fake client's returned value to updatedSigner.
+	fakeClient.mu.Lock()
+	fakeClient.value = updatedSigner
+	fakeClient.mu.Unlock()
+
+	// Wait enough for the background polling routine to fetch the new value.
+	time.Sleep(1 + time.Second + defaultSyncInterval)
+
+	// Verify that system contract's signerAddressL1 is now updated to updatedSigner.
+	sys.lock.RLock()
+	newSigner := sys.signerAddressL1
+	sys.lock.RUnlock()
+	require.Equal(t, newSigner, updatedSigner, "SignerAddressL1 should update to updatedSigner after polling")
+
+	// Now simulate authorizing with the correct local signer.
+	sys.Authorize(updatedSigner, func(acc accounts.Account, mimeType string, message []byte) ([]byte, error) {
+		// For testing, return a dummy signature.
+		return []byte("dummy_signature"), nil
+	})
+
+	// Create a dummy header for sealing.
+	header := &types.Header{
+		Number:     big.NewInt(100),
+		Extra:      make([]byte, extraSeal),
+		Time:       uint64(time.Now().Add(10 * time.Second).Unix()),
+		GasLimit:   10000000,
+		Nonce:      types.BlockNonce{}, // must be zero as per rules
+		MixDigest:  common.Hash{},      // for PoA, typically zero
+		Difficulty: big.NewInt(1),
+	}
+
+	// Construct a new block from the header using NewBlock constructor.
+	block := types.NewBlock(header, nil, nil, nil, trie.NewStackTrie(nil))
+
+	// Set up channels required for Seal.
+	results := make(chan *types.Block)
+	stop := make(chan struct{})
+
+	// Call Seal. It should succeed (i.e. return no error) because local signer now equals authorized signer.
+	err := sys.Seal(nil, block, results, stop)
+	require.NoError(t, err, "Seal should succeed when the local signer is authorized after update")
+
+	// Wait for the result from Seal's goroutine.
+	select {
+	case sealedBlock := <-results:
+		require.NotNil(t, sealedBlock, "Seal should eventually return a sealed block")
+		// Optionally, you may log or further inspect sealedBlock here.
+	case <-time.After(15 * time.Second):
+		t.Fatal("Timed out waiting for Seal to return a sealed block")
+	}
+}
+
+// fakeEthClient implements a minimal version of sync_service.EthClient for testing purposes.
+type fakeEthClient struct {
+	mu sync.Mutex
+	// value is the fixed value to return from StorageAt.
+	// We'll assume StorageAt returns a 32-byte value representing an Ethereum address.
+	value common.Address
+}
+
+// BlockNumber returns 0.
+func (f *fakeEthClient) BlockNumber(ctx context.Context) (uint64, error) {
+	return 0, nil
+}
+
+// ChainID returns a zero-value chain ID.
+func (f *fakeEthClient) ChainID(ctx context.Context) (*big.Int, error) {
+	return big.NewInt(0), nil
+}
+
+// FilterLogs returns an empty slice of logs.
+func (f *fakeEthClient) FilterLogs(ctx context.Context, q ethereum.FilterQuery) ([]types.Log, error) {
+	return []types.Log{}, nil
+}
+
+// HeaderByNumber returns nil.
+func (f *fakeEthClient) HeaderByNumber(ctx context.Context, number *big.Int) (*types.Header, error) {
+	return nil, nil
+}
+
+// SubscribeFilterLogs returns a nil subscription.
+func (f *fakeEthClient) SubscribeFilterLogs(ctx context.Context, query ethereum.FilterQuery, ch chan<- types.Log) (ethereum.Subscription, error) {
+	return nil, nil
+}
+
+// TransactionByHash returns (nil, false, nil).
+func (f *fakeEthClient) TransactionByHash(ctx context.Context, txHash common.Hash) (*types.Transaction, bool, error) {
+	return nil, false, nil
+}
+
+// BlockByHash returns nil.
+func (f *fakeEthClient) BlockByHash(ctx context.Context, hash common.Hash) (*types.Block, error) {
+	return nil, nil
+}
+
+// StorageAt returns the byte representation of f.value.
+func (f *fakeEthClient) StorageAt(ctx context.Context, account common.Address, key common.Hash, blockNumber *big.Int) ([]byte, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return f.value.Bytes(), nil
+}
diff --git a/go.mod b/go.mod
index db0e122a1d37..3ffa21e58fdc 100644
--- a/go.mod
+++ b/go.mod
@@ -21,7 +21,7 @@ require (
 	github.com/edsrzf/mmap-go v1.0.0
 	github.com/ethereum/c-kzg-4844/bindings/go v0.0.0-20230126171313-363c7d7593b4
 	github.com/fatih/color v1.7.0
-	github.com/fjl/memsize v0.0.0-20190710130421-bcb5799ab5e5
+	github.com/fjl/memsize v0.0.2
 	github.com/gballet/go-libpcsclite v0.0.0-20190607065134-2772fd86a8ff
 	github.com/go-stack/stack v1.8.1
 	github.com/golang/protobuf v1.4.3
diff --git a/go.sum b/go.sum
index 47f631beb92e..2f6680439bd9 100644
--- a/go.sum
+++ b/go.sum
@@ -136,6 +136,8 @@ github.com/fatih/color v1.7.0 h1:DkWD4oS2D8LGGgTQ6IvwJJXSL5Vp2ffcQg58nFV38Ys=
 github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5KwzbycvMj4=
 github.com/fjl/memsize v0.0.0-20190710130421-bcb5799ab5e5 h1:FtmdgXiUlNeRsoNMFlKLDt+S+6hbjVMEW6RGQ7aUf7c=
 github.com/fjl/memsize v0.0.0-20190710130421-bcb5799ab5e5/go.mod h1:VvhXpOYNQvB+uIk2RvXzuaQtkQJzzIx6lSBe1xv7hi0=
+github.com/fjl/memsize v0.0.2 h1:27txuSD9or+NZlnOWdKUxeBzTAUkWCVh+4Gf2dWFOzA=
+github.com/fjl/memsize v0.0.2/go.mod h1:VvhXpOYNQvB+uIk2RvXzuaQtkQJzzIx6lSBe1xv7hi0=
 github.com/fogleman/gg v1.2.1-0.20190220221249-0403632d5b90/go.mod h1:R/bRT+9gY/C5z7JzPU0zXsXHKM4/ayA+zqcVNZzPa1k=
 github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
 github.com/fsnotify/fsnotify v1.4.9 h1:hsms1Qyu0jgnwNXIxa+/V/PDsU6CfLf6CNO8H7IWoS4=
diff --git a/rollup/rollup_sync_service/l1client_test.go b/rollup/rollup_sync_service/l1client_test.go
index 8a42bfb3068e..397e25a29ade 100644
--- a/rollup/rollup_sync_service/l1client_test.go
+++ b/rollup/rollup_sync_service/l1client_test.go
@@ -76,4 +76,3 @@ func (m *mockEthClient) BlockByHash(ctx context.Context, hash common.Hash) (*typ
 func (m *mockEthClient) StorageAt(ctx context.Context, account common.Address, key common.Hash, blockNumber *big.Int) ([]byte, error) {
 	return nil, nil
 }
-