refactor: reuse e2e text tail helper

vincentkoc · vincentkoc · commit 5620229f9f92 · 2026-05-29T19:06:38.000+02:00
diff --git a/scripts/e2e/lib/agent-turn-output.mjs b/scripts/e2e/lib/agent-turn-output.mjs
@@ -1,4 +1,5 @@
 import fs from "node:fs";
+import { readTextFileTail, tailText } from "./text-file-utils.mjs";
 
 const ERROR_DETAIL_TAIL_BYTES = 64 * 1024;
 const REPLY_TEXT_PREVIEW_BYTES = 8 * 1024;
@@ -15,13 +16,6 @@ function textByteLength(text) {
   return Buffer.byteLength(text, "utf8");
 }
 
-function tailText(text, maxBytes = ERROR_DETAIL_TAIL_BYTES) {
-  if (textByteLength(text) <= maxBytes) {
-    return text;
-  }
-  return Buffer.from(text, "utf8").subarray(-maxBytes).toString("utf8");
-}
-
 function summarizeReplyTexts(replyTexts) {
   const previewStart = Math.max(0, replyTexts.length - REPLY_TEXT_PREVIEW_COUNT);
   const recent = replyTexts.slice(previewStart).map((text, index) => ({
@@ -32,29 +26,6 @@ function summarizeReplyTexts(replyTexts) {
   return JSON.stringify({ count: replyTexts.length, recent });
 }
 
-function readTextFileTail(file, maxBytes = ERROR_DETAIL_TAIL_BYTES) {
-  let stat;
-  try {
-    stat = fs.statSync(file);
-  } catch {
-    return "";
-  }
-  if (!stat.isFile() || stat.size <= 0) {
-    return "";
-  }
-
-  const length = Math.min(maxBytes, stat.size);
-  const start = stat.size - length;
-  const fd = fs.openSync(file, "r");
-  try {
-    const buffer = Buffer.alloc(length);
-    const bytesRead = fs.readSync(fd, buffer, 0, length, start);
-    return buffer.subarray(0, bytesRead).toString("utf8");
-  } finally {
-    fs.closeSync(fd);
-  }
-}
-
 function fileContainsPattern(file, pattern) {
   let stat;
   try {
@@ -198,7 +169,7 @@ export function assertAgentReplyContainsMarker(marker, outputPath) {
   if (replyTexts.some((text) => text.includes(marker))) {
     return;
   }
-  const outputTail = tailText(output);
+  const outputTail = tailText(output, ERROR_DETAIL_TAIL_BYTES);
   throw new Error(
     `agent reply payload did not contain marker ${marker}. Reply payload summary: ${summarizeReplyTexts(replyTexts)}. Output tail: ${outputTail}`,
   );
@@ -208,6 +179,6 @@ export function assertOpenAiRequestLogUsed(requestLogPath, label = "mock OpenAI
   if (fileContainsPattern(requestLogPath, OPENAI_REQUEST_PATH_PATTERN)) {
     return;
   }
-  const requestLogTail = readTextFileTail(requestLogPath);
+  const requestLogTail = readTextFileTail(requestLogPath, ERROR_DETAIL_TAIL_BYTES);
   throw new Error(`${label} was not used. Request log tail: ${requestLogTail}`);
 }
