diff --git a/hexutil/hexutil.go b/hexutil/hexutil.go
index f861763..5d5d235 100644
--- a/hexutil/hexutil.go
+++ b/hexutil/hexutil.go
@@ -27,9 +27,6 @@ func BigIntToHex(x *big.Int) string {
 // HexToBigInt returns the big integer representation of the given hex string.
 // The hex string may be prefixed with "0x".
 func HexToBigInt(h string) (*big.Int, error) {
-	if len(h) == 0 {
-		return big.NewInt(0), nil
-	}
 	isNeg := len(h) > 1 && h[0] == '-'
 	if isNeg {
 		h = h[1:]
diff --git a/hexutil/hexutil_test.go b/hexutil/hexutil_test.go
new file mode 100644
index 0000000..bbd4af1
--- /dev/null
+++ b/hexutil/hexutil_test.go
@@ -0,0 +1,98 @@
+package hexutil
+
+import (
+	"fmt"
+	"math/big"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBigIntToHex(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    *big.Int
+		expected string
+	}{
+		{"nil input", nil, "0x0"},
+		{"zero value", big.NewInt(0), "0x0"},
+		{"positive value", big.NewInt(26), "0x1a"},
+		{"negative value", big.NewInt(-26), "-0x1a"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, BigIntToHex(tt.input))
+		})
+	}
+}
+
+func TestHexToBigInt(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected *big.Int
+		err      error
+	}{
+		{"zero", "0x0", big.NewInt(0), nil},
+		{"zero without prefix", "0", big.NewInt(0), nil},
+		{"valid positive hex", "0x1a", big.NewInt(26), nil},
+		{"valid positive hex without prefix", "1a", big.NewInt(26), nil},
+		{"valid negative hex", "-0x1a", big.NewInt(-26), nil},
+		{"valid negative hex without prefix", "-1a", big.NewInt(-26), nil},
+		{"valid positive single char hex", "0xa", big.NewInt(10), nil},
+		{"valid negative single char hex", "-0xa", big.NewInt(-10), nil},
+		{"empty string", "", nil, fmt.Errorf("invalid hex string")},
+		{"invalid hex", "0x1g", nil, fmt.Errorf("invalid hex string")},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := HexToBigInt(tt.input)
+			assert.Equal(t, tt.err, err)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func TestBytesToHex(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    []byte
+		expected string
+	}{
+		{"empty bytes", []byte{}, "0x"},
+		{"non-empty bytes", []byte("abc"), "0x616263"},
+		{"bytes with zeros", []byte{0, 1, 2}, "0x000102"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.expected, BytesToHex(tt.input))
+		})
+	}
+}
+
+func TestHexToBytes(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected []byte
+		err      error
+	}{
+		{"empty string", "", []byte{}, nil},
+		{"empty data", "0x", []byte{}, nil},
+		{"valid hex", "0x616263", []byte("abc"), nil},
+		{"valid hex without prefix", "616263", []byte("abc"), nil},
+		{"single zero", "0", []byte{0}, nil},
+		{"invalid hex", "0x1", nil, fmt.Errorf("invalid hex string, length must be even")},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := HexToBytes(tt.input)
+			assert.Equal(t, tt.err, err)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}