From 7bd6152ccafc06fdd273dd16b836f620d2c62188 Mon Sep 17 00:00:00 2001
From: kakkokari-gtyih <67428053+kakkokari-gtyih@users.noreply.github.com>
Date: Fri, 31 Jul 2026 19:58:41 +0900
Subject: [PATCH] =?UTF-8?q?test(backend):=20LogNormalizer=E3=81=AE?=
 =?UTF-8?q?=E6=96=87=E5=AD=97=E5=88=97=E5=88=87=E3=82=8A=E8=A9=B0=E3=82=81?=
 =?UTF-8?q?=E3=81=AB=E5=A2=83=E7=95=8C=E3=82=B1=E3=83=BC=E3=82=B9=E3=81=AE?=
 =?UTF-8?q?=E3=83=86=E3=82=B9=E3=83=88=E3=82=92=E8=BF=BD=E5=8A=A0?=
MIME-Version: 1.0
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線形走査への変更に対し、2/3/4バイト文字が切り詰め境界に来る場合と、
接尾辞が上限に収まらない場合の挙動を検証する。

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
---
 .../test/unit/logging/LogNormalizer.ts        | 38 +++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/packages/backend/test/unit/logging/LogNormalizer.ts b/packages/backend/test/unit/logging/LogNormalizer.ts
index b183f03fcd..24efd14909 100644
--- a/packages/backend/test/unit/logging/LogNormalizer.ts
+++ b/packages/backend/test/unit/logging/LogNormalizer.ts
@@ -115,6 +115,44 @@ describe('LogNormalizer', () => {
 		expect(JSON.stringify(normalized.value)).not.toContain('�');
 	});
 
+	test('truncates at UTF-8 character boundaries for every character width', () => {
+		const suffix = '…[Truncated]';
+		const suffixBytes = Buffer.byteLength(suffix, 'utf8');
+
+		// 2 / 3 / 4バイト文字それぞれについて、切り詰め位置が文字の途中に落ちる場合を網羅する
+		const cases = [
+			['é', 2], // é
+			['あ', 3], // あ
+			['\u{1f600}', 4], // 😀 (サロゲート対)
+		] as const;
+
+		for (const [char, charBytes] of cases) {
+			for (let slack = 0; slack < charBytes; slack++) {
+				const maxStringBytes = suffixBytes + charBytes + slack;
+				const normalized = normalizeLogAttributes(
+					{ value: char.repeat(20) },
+					{ limits: { maxStringBytes, maxBytes: 4096 } },
+				).value as string;
+
+				expect(Buffer.byteLength(normalized, 'utf8')).toBeLessThanOrEqual(maxStringBytes);
+				expect(normalized).toBe(char + suffix);
+				// サロゲート対の分割などで不正なUTF-8になっていないこと
+				expect(Buffer.from(normalized, 'utf8').toString('utf8')).toBe(normalized);
+			}
+		}
+	});
+
+	test('drops the truncation suffix when it does not fit within the byte limit', () => {
+		const normalized = normalizeLogAttributes(
+			{ value: 'あ'.repeat(20) },
+			{ limits: { maxStringBytes: 10, maxBytes: 4096 } },
+		).value as string;
+
+		// 接尾辞(14バイト)が上限に収まらないので、接尾辞なしで文字境界まで切り詰める
+		expect(normalized).toBe('あ'.repeat(3));
+		expect(Buffer.byteLength(normalized, 'utf8')).toBeLessThanOrEqual(10);
+	});
+
 	test('serializes Error and its cause consistently', () => {
 		const cause = new Error('root cause');
 		const error = new TypeError('outer error', { cause });