test(message-parser): add tests for joinEmoji behavior

.changeset/message-parser-joinEmoji-tests.md

@@ -0,0 +1,5 @@
+---
+"@rocket.chat/message-parser": patch
+---
+
+Add test coverage for joinEmoji behavior through reducePlainTexts

packages/message-parser/tests/joinEmoji.test.ts

@@ -0,0 +1,32 @@
+import { plain, emoji, reducePlainTexts } from '../src/utils';
+
+describe('joinEmoji behavior through reducePlainTexts', () => {
+	it('keeps emoji when alone', () => {
+		const result = reducePlainTexts([emoji('smile')]);
+		expect(result[0].type).toBe('EMOJI');
+	});
+
+	it('merges consecutive plain texts', () => {
+		const result = reducePlainTexts([
+			plain('hello '),
+			plain('world'),
+		]);
+
+		expect(result).toHaveLength(1);
+		expect(result[0]).toMatchObject({ type: 'PLAIN_TEXT', value: 'hello world' });
+	});
+
+	it('converts emoji with plain text neighbors to shortCode and merges', () => {
+		const result = reducePlainTexts([
+			plain('hello'),
+			emoji('smile'),
+			plain('world'),
+		]);
+
+		expect(result).toHaveLength(1);
+		expect(result[0]).toMatchObject({
+			type: 'PLAIN_TEXT',
+			value: 'hello:smile:world',
+		});
+	});
+});