test(backend): restore more unit tests (#9994)

packages/backend/test/unit/extract-mentions.ts

@@ -0,0 +1,42 @@
+import * as assert from 'assert';
+
+import { parse } from 'mfm-js';
+import { extractMentions } from '@/misc/extract-mentions.js';
+
+describe('Extract mentions', () => {
+	test('simple', () => {
+		const ast = parse('@foo @bar @baz');
+		const mentions = extractMentions(ast);
+		assert.deepStrictEqual(mentions, [{
+			username: 'foo',
+			acct: '@foo',
+			host: null,
+		}, {
+			username: 'bar',
+			acct: '@bar',
+			host: null,
+		}, {
+			username: 'baz',
+			acct: '@baz',
+			host: null,
+		}]);
+	});
+
+	test('nested', () => {
+		const ast = parse('@foo **@bar** @baz');
+		const mentions = extractMentions(ast);
+		assert.deepStrictEqual(mentions, [{
+			username: 'foo',
+			acct: '@foo',
+			host: null,
+		}, {
+			username: 'bar',
+			acct: '@bar',
+			host: null,
+		}, {
+			username: 'baz',
+			acct: '@baz',
+			host: null,
+		}]);
+	});
+});