refactor: replace Jest with bun

packages/game/test/mockFileChecker.ts

@@ -0,0 +1,22 @@
+import type { IFileExistenceChecker, IFileInput } from '../schema'
+
+export class MockFileChecker implements IFileExistenceChecker {
+  private files: IFileInput[] = [
+    {
+      path: '/home/user/hello.txt',
+      type: 'file',
+    },
+    {
+      path: '/home/user/world.txt',
+      type: 'file',
+    },
+    {
+      path: '/home/user/Downloads',
+      type: 'directory',
+    },
+  ]
+
+  async exists(file: IFileInput): Promise<boolean> {
+    return this.files.some((f) => f.path === file.path && f.type === file.type)
+  }
+}