reduce reproduction code

Author: mizdra

fixtures/file.txt

@@ -0,0 +1 @@
+2

packages/codegen/src/runner.test.ts

@@ -1,9 +1,9 @@
 import assert from 'node:assert';
 import { writeFile } from 'node:fs/promises';
+import { join } from 'node:path';
 import { platform } from 'node:process';
 import chokidar from 'chokidar';
 import { describe, test, vi } from 'vitest';
-import { createIFF } from './test/fixture.js';
 
 async function sleep(ms: number): Promise<void> {
   // eslint-disable-next-line no-promise-executor-return
@@ -17,21 +17,19 @@ async function waitForWatcherEmitAndReportDiagnostics(): Promise<void> {
 
 describe('runCMKInWatchMode', () => {
   test('reports system error occurs during watching', async () => {
-    const iff = await createIFF({
-      'tsconfig.json': '{}',
-      'src/a.module.css': '.a_1 { color: red; }',
-    });
+    const fixturePath = join(process.cwd(), 'fixtures');
+    const textFilePath = join(fixturePath, 'file.txt');
 
     // On macOS, chokidar may detect 'add' events for files added before watching starts.
     // To avoid test flakiness, wait for a short time before starting the watcher.
     await sleep(100);
 
     const { promise, resolve } = Promise.withResolvers<void>();
     chokidar
-      .watch(iff.rootDir, { ignoreInitial: true })
+      .watch(fixturePath, { ignoreInitial: true })
       .on('change', (fileName) => {
         console.log('change event: ', fileName);
-        if (fileName.endsWith('a.module.css')) {
+        if (fileName.endsWith('file.txt')) {
           globalThis.changeCount++;
         }
       })
@@ -49,13 +47,13 @@ describe('runCMKInWatchMode', () => {
     globalThis.changeCount = 0;
 
     console.log('update a.module.css');
-    await writeFile(iff.join('src/a.module.css'), '.a_1 { color: blue; }');
+    await writeFile(textFilePath, '1');
     await vi.waitFor(() => {
       assert(globalThis.changeCount === 1, `Expected changeCount to be 1, but got ${globalThis.changeCount}`);
     });
 
     console.log('update a.module.css');
-    await writeFile(iff.join('src/a.module.css'), '.a_1 { color: yellow; }');
+    await writeFile(textFilePath, '2');
     await waitForWatcherEmitAndReportDiagnostics();
     assert(globalThis.changeCount === 2, `Expected changeCount to be 2, but got ${globalThis.changeCount}`);
   });