diff --git a/internal/json_store_test.go b/internal/json_store_test.go
index 6ec0539..93856fe 100644
--- a/internal/json_store_test.go
+++ b/internal/json_store_test.go
@@ -9,6 +9,7 @@ import (
 	"path/filepath"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/nmoniz/any2anexoj/internal"
 	"github.com/nmoniz/any2anexoj/internal/mocks"
@@ -84,13 +85,25 @@ func TestJSONStore_RoundTrip(t *testing.T) {
 	// confirming the inline form is parseable guards against accidentally
 	// double-encoding it again in the future).
 	var parsed struct {
-		Queues map[string][]struct {
+		Latest   time.Time `json:"latest"`
+		Earliest time.Time `json:"earliest"`
+		Queues   map[string][]struct {
 			RecordData json.RawMessage `json:"record_data"`
 		} `json:"queues"`
 	}
 	if err := json.Unmarshal(data, &parsed); err != nil {
 		t.Fatalf("saved state file is not valid JSON: %v", err)
 	}
+
+	// The latest/earliest bounds must be persisted alongside the queues.
+	// Every record in this test returns testRecordTime, so both bounds must
+	// equal it exactly.
+	if !parsed.Latest.Equal(testRecordTime) {
+		t.Errorf("state latest = %v; want %v", parsed.Latest, testRecordTime)
+	}
+	if !parsed.Earliest.Equal(testRecordTime) {
+		t.Errorf("state earliest = %v; want %v", parsed.Earliest, testRecordTime)
+	}
 	for symbol, lots := range parsed.Queues {
 		for i, lot := range lots {
 			if len(lot.RecordData) == 0 {
@@ -341,13 +354,20 @@ func TestNewJSONStore_ValidatesArguments(t *testing.T) {
 	}
 }
 
-// newRecord builds a MockRecord whose Symbol() returns the given symbol.
-// The JSONStore only reads Symbol() off the loaded Record during tests
-// (quantity/price/filled come from the persisted struct fields), so all
-// other Record methods can be left as default-mocked values.
+// testRecordTime is the deterministic timestamp returned by every record
+// built in this file. Using a fixed value keeps the latest/earliest bounds
+// written by JSONStore.Save predictable and assertable.
+var testRecordTime = time.Date(2024, 6, 15, 12, 0, 0, 0, time.UTC)
+
+// newRecord builds a MockRecord whose Symbol() returns the given symbol and
+// whose Timestamp() returns testRecordTime. The JSONStore only reads Symbol()
+// and Timestamp() off the Record during tests (quantity/price/filled come
+// from the persisted struct fields), so all other Record methods can be left
+// as default-mocked values.
 func newRecord(ctrl *gomock.Controller, symbol string) *mocks.MockRecord {
 	r := mocks.NewMockRecord(ctrl)
 	r.EXPECT().Symbol().Return(symbol).AnyTimes()
+	r.EXPECT().Timestamp().Return(testRecordTime).AnyTimes()
 	return r
 }