implemented enlarged emoji rendering for chat messages containing up to three emojis

test/utils/emoji_detection_test.dart

@@ -0,0 +1,62 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/utils/emoji_detection.dart';
+
+void main() {
+  group('standaloneEmojiFontSize', () {
+    test('returns null for empty or whitespace-only text', () {
+      expect(standaloneEmojiFontSize(''), isNull);
+      expect(standaloneEmojiFontSize('   '), isNull);
+    });
+
+    test('returns null for plain text', () {
+      expect(standaloneEmojiFontSize('Hallo'), isNull);
+      expect(standaloneEmojiFontSize('ok'), isNull);
+    });
+
+    test('returns null when emoji is mixed with text', () {
+      expect(standaloneEmojiFontSize('Hallo 😀'), isNull);
+      expect(standaloneEmojiFontSize('😀 super'), isNull);
+    });
+
+    test('enlarges a single emoji the most', () {
+      expect(standaloneEmojiFontSize('😀'), 34);
+      expect(standaloneEmojiFontSize('👍'), 34);
+    });
+
+    test('enlarges up to three emojis at the largest size', () {
+      expect(standaloneEmojiFontSize('😀😀😀'), 34);
+      expect(standaloneEmojiFontSize('😀 😀 😀'), 34);
+    });
+
+    test('does not enlarge more than three emojis', () {
+      expect(standaloneEmojiFontSize('😀😀😀😀'), isNull);
+      expect(standaloneEmojiFontSize('😀😀😀😀😀😀'), isNull);
+    });
+
+    test('handles ZWJ sequences as a single emoji', () {
+      // Family emoji: multiple codepoints joined via ZWJ → one cluster.
+      expect(standaloneEmojiFontSize('👨‍👩‍👧‍👦'), 34);
+    });
+
+    test('handles skin-tone modified emoji as a single emoji', () {
+      expect(standaloneEmojiFontSize('👍🏽'), 34);
+    });
+
+    test('handles emoji with variation selectors', () {
+      expect(standaloneEmojiFontSize('❤️'), 34);
+      expect(standaloneEmojiFontSize('⭐'), 34);
+    });
+
+    test('handles keycap emoji', () {
+      expect(standaloneEmojiFontSize('1️⃣'), 34);
+    });
+
+    test('handles flag emoji (regional indicators)', () {
+      expect(standaloneEmojiFontSize('🇩🇪'), 34);
+    });
+
+    test('bare digits without keycap are not emoji', () {
+      expect(standaloneEmojiFontSize('123'), isNull);
+    });
+  });
+}