test(ts): add assertion so we don't accidentally bump TS again @W-18978621

packages/lwc/__tests__/typescript.spec.ts

@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2025, Salesforce, Inc.
+ * All rights reserved.
+ * SPDX-License-Identifier: MIT
+ * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
+ */
+import { version } from 'typescript';
+import { expect, test } from 'vitest';
+
+// This is more of a repo configuration test than a test of the `lwc` package,
+// but we don't really have a place to catch accidental foot-gunnery.
+
+test('TypeScript version should not change', () => {
+    // Because we are a library, bumping the version of TypeScript is a
+    // potentially breaking change. Code that may compile using our version may
+    // result in type errors in different versions (e.g. using new syntax).
+    expect(version, 'TypeScript version should only change for major releases of LWC').toBe(
+        '5.8.2'
+    );
+});