fix(tests): improve test reliability and performance (#8395)

packages/core/src/utils/fileUtils.test.ts

@@ -15,6 +15,7 @@ import {
 } from 'vitest';
 
 import * as actualNodeFs from 'node:fs'; // For setup/teardown
+import fs from 'node:fs';
 import fsPromises from 'node:fs/promises';
 import path from 'node:path';
 import os from 'node:os';
@@ -954,22 +955,30 @@ describe('fileUtils', () => {
     });
 
     it('should return an error if the file size exceeds 20MB', async () => {
-      // Create a file just over 20MB
-      const twentyOneMB = 21 * 1024 * 1024;
-      const buffer = Buffer.alloc(twentyOneMB, 0x61); // Fill with 'a'
-      actualNodeFs.writeFileSync(testTextFilePath, buffer);
+      // Create a small test file
+      actualNodeFs.writeFileSync(testTextFilePath, 'test content');
 
-      const result = await processSingleFileContent(
-        testTextFilePath,
-        tempRootDir,
-        new StandardFileSystemService(),
-      );
+      // Spy on fs.promises.stat to return a large file size
+      const statSpy = vi.spyOn(fs.promises, 'stat').mockResolvedValueOnce({
+        size: 21 * 1024 * 1024,
+        isDirectory: () => false,
+      } as fs.Stats);
 
-      expect(result.error).toContain('File size exceeds the 20MB limit');
-      expect(result.returnDisplay).toContain(
-        'File size exceeds the 20MB limit',
-      );
-      expect(result.llmContent).toContain('File size exceeds the 20MB limit');
+      try {
+        const result = await processSingleFileContent(
+          testTextFilePath,
+          tempRootDir,
+          new StandardFileSystemService(),
+        );
+
+        expect(result.error).toContain('File size exceeds the 20MB limit');
+        expect(result.returnDisplay).toContain(
+          'File size exceeds the 20MB limit',
+        );
+        expect(result.llmContent).toContain('File size exceeds the 20MB limit');
+      } finally {
+        statSpy.mockRestore();
+      }
     });
   });
 });