Revert "remove index test"

This reverts commit 10c63f5.

Author: devjiwonchoi

test/development/typescript-plugin/index.test.ts

@@ -0,0 +1,18 @@
+import type { PluginLanguageService } from './test-utils'
+import { getPluginLanguageService } from './test-utils'
+
+describe('typescript-plugin', () => {
+  let languageService: PluginLanguageService
+
+  beforeAll(() => {
+    languageService = getPluginLanguageService(__dirname)
+  })
+
+  it('should be able to get the language service', () => {
+    expect(languageService).toBeDefined()
+    const capturedLogs = languageService.getCapturedLogs()
+    expect(capturedLogs).toContain(
+      '[next] Initialized Next.js TypeScript plugin'
+    )
+  })
+})