test: capture remaining checkout race regressions

scripts/install-hooks.test.mjs

@@ -110,6 +110,34 @@ test('a mismatched complete hook set fails loudly instead of reporting a stale i
   assert.equal(await readFile(activeShim, 'utf8'), 'old-complete');
 });
 
+test('a competing successful installer is not removed by the losing process', async () => {
+  const root = await fixture('concurrent');
+  const activeShim = path.join(root, '.husky', '_', 'h');
+  let restored = false;
+
+  await assert.rejects(
+    installHooks({
+      root,
+      quarantineRoot: path.join(fixtureRoot, 'concurrent-quarantine'),
+      runHusky: async (stagingHooks) => {
+        await mkdir(path.join(stagingHooks, '_'), { recursive: true });
+        await writeFile(path.join(stagingHooks, '_', 'h'), 'ours');
+        await mkdir(path.dirname(activeShim), { recursive: true });
+        await writeFile(activeShim, 'peer');
+      },
+      activateHooks: async () => {},
+      readHooksPath: async () => null,
+      restoreHooksPath: async () => {
+        restored = true;
+      },
+    }),
+    /Hook installation failed/,
+  );
+
+  assert.equal(await readFile(activeShim, 'utf8'), 'peer');
+  assert.equal(restored, false);
+});
+
 test('an explicit interactive HUSKY=0 opt-out preserves existing hooks without running installer', async () => {
   const root = await fixture('disabled');
   const activeShim = path.join(root, '.husky', '_', 'h');

scripts/preflight.test.mjs

@@ -3,7 +3,7 @@ import { chmod, mkdir, rm, symlink, utimes, writeFile } from 'node:fs/promises';
 import path from 'node:path';
 import test from 'node:test';
 
-import { runPreflight } from './preflight.mjs';
+import { runPreflight, sourceFingerprint } from './preflight.mjs';
 
 const fixtureRoot = path.join(process.cwd(), '.mosaic-test-work', `preflight-${process.pid}`);
 
@@ -83,18 +83,13 @@ test('foreign-owned generated Next state is identified separately from source er
   assert.match(result.message, /foreign-owned/);
 });
 
-test('stale generated Next state is identified separately from source errors', async () => {
+test('a generated marker mismatch is identified separately from source errors', async () => {
   const root = await fixture('stale-next');
   await installRequiredBins(root);
   const generated = path.join(root, 'apps', 'web', '.next', 'types', 'validator.ts');
   await mkdir(path.dirname(generated), { recursive: true });
   await writeFile(generated, 'stale generated output');
-  const old = new Date('2020-01-01T00:00:00Z');
-  await utimes(generated, old, old);
-  const fresh = path.join(root, 'apps', 'web', '.next', 'types', 'routes.ts');
-  await writeFile(fresh, 'fresh generated output');
-  const future = new Date('2030-01-01T00:00:00Z');
-  await utimes(fresh, future, future);
+  await writeFile(path.join(root, 'apps', 'web', '.next', '.mosaic-source-hash'), 'old-source');
 
   const result = await runPreflight({ root });
   assert.equal(result.code, 43);
@@ -102,3 +97,20 @@ test('stale generated Next state is identified separately from source errors', a
   assert.match(result.message, /apps\/web\/\.next/);
   assert.match(result.message, /pnpm clean:generated/);
 });
+
+test('a matching generation marker accepts incremental output with mixed mtimes', async () => {
+  const root = await fixture('incremental-next');
+  await installRequiredBins(root);
+  const generated = path.join(root, 'apps', 'web', '.next', 'types', 'validator.ts');
+  await mkdir(path.dirname(generated), { recursive: true });
+  await writeFile(generated, 'unchanged generated output');
+  await utimes(generated, new Date('2020-01-01T00:00:00Z'), new Date('2020-01-01T00:00:00Z'));
+  const fresh = path.join(root, 'apps', 'web', '.next', 'types', 'routes.ts');
+  await writeFile(fresh, 'fresh generated output');
+  await writeFile(
+    path.join(root, 'apps', 'web', '.next', '.mosaic-source-hash'),
+    await sourceFingerprint(root),
+  );
+
+  assert.deepEqual(await runPreflight({ root }), { code: 0, message: 'checkout preflight passed' });
+});