userfront&backend test coverage 추가

backend/internal/pagination/cursor_test.go

@@ -1,10 +1,13 @@
 package pagination
 
 import (
+	"encoding/base64"
 	"testing"
 	"time"
 
 	"github.com/stretchr/testify/require"
+	"gorm.io/driver/postgres"
+	"gorm.io/gorm"
 )
 
 type testItem struct {
@@ -53,3 +56,87 @@ func TestSortByKeyDescUsesIDAsTieBreaker(t *testing.T) {
 		items[2].id,
 	})
 }
+
+func TestEncodeReturnsEmptyForInvalidInput(t *testing.T) {
+	require.Empty(t, Encode(time.Time{}, "id"))
+	require.Empty(t, Encode(time.Now(), " "))
+}
+
+func TestDecodeRejectsInvalidCursor(t *testing.T) {
+	t.Run("blank cursor is nil", func(t *testing.T) {
+		cursor, err := Decode(" ")
+		require.NoError(t, err)
+		require.Nil(t, cursor)
+	})
+
+	t.Run("invalid base64 returns error", func(t *testing.T) {
+		cursor, err := Decode("not base64")
+		require.Error(t, err)
+		require.Nil(t, cursor)
+	})
+
+	t.Run("invalid json returns error", func(t *testing.T) {
+		raw := base64.RawURLEncoding.EncodeToString([]byte("{invalid"))
+		cursor, err := Decode(raw)
+		require.Error(t, err)
+		require.Nil(t, cursor)
+	})
+
+	t.Run("missing timestamp returns invalid cursor", func(t *testing.T) {
+		raw := base64.RawURLEncoding.EncodeToString([]byte(`{"id":"abc"}`))
+		cursor, err := Decode(raw)
+		require.EqualError(t, err, "invalid cursor")
+		require.Nil(t, cursor)
+	})
+
+	t.Run("missing id returns invalid cursor", func(t *testing.T) {
+		raw := base64.RawURLEncoding.EncodeToString([]byte(`{"timestamp":"2026-05-29T00:00:00Z"}`))
+		cursor, err := Decode(raw)
+		require.EqualError(t, err, "invalid cursor")
+		require.Nil(t, cursor)
+	})
+}
+
+func TestComesAfter(t *testing.T) {
+	now := time.Date(2026, 5, 29, 8, 0, 0, 0, time.UTC)
+	cursor := &Cursor{Timestamp: now, ID: "m"}
+
+	require.True(t, ComesAfter(now, "id", nil))
+	require.True(t, ComesAfter(now.Add(-time.Second), "z", cursor))
+	require.True(t, ComesAfter(now, "a", cursor))
+	require.False(t, ComesAfter(now.Add(time.Second), "a", cursor))
+	require.False(t, ComesAfter(now, "z", cursor))
+}
+
+func TestPageByCursorReturnsDecodeError(t *testing.T) {
+	items := []testItem{{id: "a", createdAt: time.Now()}}
+
+	page, nextCursor, err := PageByCursor(items, 10, "not base64", func(item testItem) (time.Time, string) {
+		return item.createdAt, item.id
+	})
+
+	require.Error(t, err)
+	require.Nil(t, page)
+	require.Empty(t, nextCursor)
+}
+
+func TestApplyCreatedAtIDCursor(t *testing.T) {
+	db, err := gorm.Open(postgres.New(postgres.Config{
+		DSN: "host=localhost user=test dbname=test sslmode=disable",
+	}), &gorm.Config{
+		DryRun:               true,
+		DisableAutomaticPing: true,
+	})
+	require.NoError(t, err)
+
+	require.Same(t, db, ApplyCreatedAtIDCursor(db, nil, "created_at", "id"))
+
+	cursor := &Cursor{
+		Timestamp: time.Date(2026, 5, 29, 8, 0, 0, 0, time.UTC),
+		ID:        "cursor-id",
+	}
+	query := ApplyCreatedAtIDCursor(db.Model(&struct{}{}), cursor, "created_at", "id").Find(&[]struct{}{})
+
+	require.Contains(t, query.Statement.SQL.String(), "created_at < $1 OR (created_at = $2 AND id < $3)")
+	require.Equal(t, []any{cursor.Timestamp, cursor.Timestamp, cursor.ID}, query.Statement.Vars)
+}