test: add unit tests for "truncateMessage"

src/core/ws/utils/truncateMessage.test.ts

@@ -0,0 +1,12 @@
+import { truncateMessage } from './truncateMessage'
+
+it('returns a short string as-is', () => {
+  expect(truncateMessage('')).toBe('')
+  expect(truncateMessage('hello')).toBe('hello')
+})
+
+it('truncates a long string', () => {
+  expect(truncateMessage('this is a very long string')).toBe(
+    'this is a very long stri…',
+  )
+})