test(mcp): make checkout/reviewComments tests offline (fixture-driven) (#575)

`mcp/checkout.test.ts` and `mcp/reviewComments.test.ts` previously hit
live GitHub on every run via `acquireNewToken()`, requiring `GH_TOKEN`
or `GITHUB_APP_ID` + `GITHUB_PRIVATE_KEY` in the env. that made them:

- cred-gated — the action runtime filters `_KEY$` / `_TOKEN$` from
  subprocess env, so the husky pre-push hook (which runs
  `pnpm -r test`) blocked Pullfrog agents from pushing branches. issues
  #562, #563, #564, #566 all hit this exact blocker and never got their
  fixes pushed.
- non-deterministic and slow (network round-trips for a snapshot test).

both tests are really snapshot tests of pure formatters
(`formatFilesWithLineNumbers`, plus `parseFilePatches` /
`buildThreadBlocks` / `formatReviewThreads` for review data). the live
fetches were just an inefficient way to obtain fixtures.

changes:

1. extract a pure `formatReviewData({ review, threads, prFiles, ... })`
   from `getReviewData` in `mcp/reviewComments.ts`. `getReviewData`
   becomes thin orchestration: fetch + call formatter. preserves the
   "skip listFiles when no threads" perf optimization.

2. add `action/mcp/__fixtures__/` with checked-in JSON captures for the
   three fixture test cases (pullfrog/test-repo#1 listFiles,
   pullfrog/scratch#49 review 3485940013, pullfrog/scratch#64 review
   3531000326). ~14KB total. fixtures store only the fields the
   formatter reads — volatile fields (sha, blob_url, etc.) are dropped.

3. rewrite both test files to load the fixtures and call the pure
   formatters directly. snapshot keys updated; snapshot content
   unchanged (verified by running existing snapshots against the
   refactored tests).

4. add `action/scripts/refresh-test-fixtures.ts` to re-fetch the
   fixtures from live GitHub on demand:
   `node action/scripts/refresh-test-fixtures.ts` (with creds in
   `.env` or env). re-run when the GitHub API response shape changes
   and review the snapshot diff.

trade-off: a silent change to GitHub's `pulls.listFiles` /
`pulls.getReview` / GraphQL `reviewThreads` response shape would no
longer break this test on every push. that tradeoff is worth it: shape
drift on those endpoints is rare (years between changes), and a
dedicated cron that runs the refresh script and opens a PR on diff is
a far better signal than a flaky cred-gated pre-push hook.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/refresh-test-fixtures.ts

@@ -0,0 +1,161 @@
+#!/usr/bin/env node
+/**
+ * refresh checked-in test fixtures for mcp/checkout.test.ts and
+ * mcp/reviewComments.test.ts.
+ *
+ * those tests used to hit live GitHub on every run, which made them
+ * cred-gated (GH_TOKEN or GITHUB_APP_ID + GITHUB_PRIVATE_KEY) and
+ * non-deterministic. they now read from action/mcp/__fixtures__/*.json,
+ * which this script regenerates on demand.
+ *
+ * run with creds set (locally via .env, or in a CI cron with secrets):
+ *
+ *   GH_TOKEN=… node action/scripts/refresh-test-fixtures.ts
+ *   # or
+ *   GITHUB_APP_ID=… GITHUB_PRIVATE_KEY=… node action/scripts/refresh-test-fixtures.ts
+ *
+ * commit the resulting fixture changes; review the diff before merging
+ * (anything unexpected indicates real GitHub API drift).
+ */
+
+import { mkdirSync, writeFileSync } from "node:fs";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+import { Octokit } from "@octokit/rest";
+import { config as loadDotenv } from "dotenv";
+import {
+  REVIEW_THREADS_QUERY,
+  type ReviewThread,
+  type ReviewThreadsQueryResponse,
+} from "../mcp/reviewComments.ts";
+import { acquireNewToken } from "../utils/github.ts";
+
+const scriptDir = dirname(fileURLToPath(import.meta.url));
+const repoRoot = resolve(scriptDir, "../..");
+const fixturesDir = resolve(scriptDir, "../mcp/__fixtures__");
+
+loadDotenv({ path: resolve(repoRoot, ".env") });
+
+type DiffFixture = {
+  owner: string;
+  name: string;
+  pullNumber: number;
+  files: unknown;
+};
+
+type ReviewFixture = {
+  owner: string;
+  name: string;
+  pullNumber: number;
+  reviewId: number;
+  review: { body: string | null | undefined; user: { login: string } | null | undefined };
+  threads: ReviewThread[];
+  prFiles: Array<{ filename: string; patch?: string | undefined }>;
+};
+
+const DIFF_TARGETS: Array<Pick<DiffFixture, "owner" | "name" | "pullNumber">> = [
+  { owner: "pullfrog", name: "test-repo", pullNumber: 1 },
+];
+
+const REVIEW_TARGETS: Array<Pick<ReviewFixture, "owner" | "name" | "pullNumber" | "reviewId">> = [
+  { owner: "pullfrog", name: "scratch", pullNumber: 49, reviewId: 3485940013 },
+  { owner: "pullfrog", name: "scratch", pullNumber: 64, reviewId: 3531000326 },
+];
+
+async function getToken(): Promise<string> {
+  if (process.env.GH_TOKEN) return process.env.GH_TOKEN;
+  return await acquireNewToken();
+}
+
+async function refreshDiffFixture(
+  octokit: Octokit,
+  target: (typeof DIFF_TARGETS)[number]
+): Promise<void> {
+  const files = await octokit.paginate(octokit.rest.pulls.listFiles, {
+    owner: target.owner,
+    repo: target.name,
+    pull_number: target.pullNumber,
+    per_page: 100,
+  });
+  const fixture: DiffFixture = { ...target, files };
+  const path = resolve(
+    fixturesDir,
+    `${target.owner}-${target.name}-pr-${target.pullNumber}.diff.json`
+  );
+  writeFileSync(path, `${JSON.stringify(fixture, null, 2)}\n`);
+  console.log(`wrote ${path}`);
+}
+
+async function refreshReviewFixture(
+  octokit: Octokit,
+  target: (typeof REVIEW_TARGETS)[number]
+): Promise<void> {
+  const [review, threadsResp] = await Promise.all([
+    octokit.rest.pulls.getReview({
+      owner: target.owner,
+      repo: target.name,
+      pull_number: target.pullNumber,
+      review_id: target.reviewId,
+    }),
+    octokit.graphql<ReviewThreadsQueryResponse>(REVIEW_THREADS_QUERY, {
+      owner: target.owner,
+      name: target.name,
+      prNumber: target.pullNumber,
+    }),
+  ]);
+
+  const allThreads = threadsResp.repository?.pullRequest?.reviewThreads?.nodes ?? [];
+  const threads = allThreads.filter((thread): thread is ReviewThread => {
+    if (!thread?.comments?.nodes) return false;
+    return thread.comments.nodes.some((c) => c?.pullRequestReview?.databaseId === target.reviewId);
+  });
+
+  // skip listFiles entirely when there are no threads — prFiles is only
+  // used for thread blocks, so an empty array short-circuits in the
+  // formatter. mirrors getReviewData's runtime perf optimization and
+  // keeps body-only-review fixtures small.
+  const prFiles =
+    threads.length > 0
+      ? await octokit.paginate(octokit.rest.pulls.listFiles, {
+          owner: target.owner,
+          repo: target.name,
+          pull_number: target.pullNumber,
+          per_page: 100,
+        })
+      : [];
+
+  // strip prFiles down to the fields the formatter actually reads. keeps
+  // fixtures small and avoids capturing volatile fields (sha, blob_url,
+  // contents_url, etc.) that would churn unrelated to formatter behavior.
+  const trimmedFiles = prFiles.map((f) => ({
+    filename: f.filename,
+    ...(f.patch ? { patch: f.patch } : {}),
+  }));
+
+  const fixture: ReviewFixture = {
+    ...target,
+    review: {
+      body: review.data.body,
+      user: review.data.user ? { login: review.data.user.login } : null,
+    },
+    threads,
+    prFiles: trimmedFiles,
+  };
+  const path = resolve(
+    fixturesDir,
+    `${target.owner}-${target.name}-pr-${target.pullNumber}-review-${target.reviewId}.json`
+  );
+  writeFileSync(path, `${JSON.stringify(fixture, null, 2)}\n`);
+  console.log(`wrote ${path}`);
+}
+
+async function main(): Promise<void> {
+  const token = await getToken();
+  const octokit = new Octokit({ auth: token });
+  mkdirSync(fixturesDir, { recursive: true });
+
+  for (const t of DIFF_TARGETS) await refreshDiffFixture(octokit, t);
+  for (const t of REVIEW_TARGETS) await refreshReviewFixture(octokit, t);
+}
+
+await main();