TF-3416 Handle download attachment in EML previewer on mobile

test/features/email/parsing_attachment_by_uri_test.dart

@@ -0,0 +1,63 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:tmail_ui_user/features/email/presentation/utils/email_utils.dart';
+
+void main() {
+  group('parsingAttachmentByUri', () {
+    test('should parse a valid URI and return an Attachment object', () {
+      final uri = Uri.parse(
+        'attachment:blobId?name=testfile.txt&size=1024&type=text/plain',
+      );
+
+      final attachment = EmailUtils.parsingAttachmentByUri(uri);
+
+      expect(attachment, isNotNull);
+      expect(attachment!.blobId?.value, 'blobId');
+      expect(attachment.name, 'testfile.txt');
+      expect(attachment.size?.value, 1024);
+      expect(attachment.type?.toString(), 'text/plain');
+    });
+
+    test('should return null for an invalid URI', () {
+      final uri = Uri.parse('https://example.com');
+
+      final attachment = EmailUtils.parsingAttachmentByUri(uri);
+
+      expect(attachment, isNull);
+    });
+
+    test('should handle missing optional parameters gracefully', () {
+      final uri = Uri.parse('attachment:blobId?name=testfile.txt');
+
+      final attachment = EmailUtils.parsingAttachmentByUri(uri);
+
+      expect(attachment, isNotNull);
+      expect(attachment!.blobId?.value, 'blobId');
+      expect(attachment.name, 'testfile.txt');
+      expect(attachment.size, isNull);
+      expect(attachment.type, isNull);
+    });
+
+    test('should handle invalid size parameter gracefully', () {
+      final uri = Uri.parse(
+        'attachment:blobId?name=testfile.txt&size=invalid',
+      );
+
+      final attachment = EmailUtils.parsingAttachmentByUri(uri);
+
+      expect(attachment, isNull);
+    });
+
+    test('should handle empty type parameter gracefully', () {
+      final uri = Uri.parse(
+        'attachment:blobId?name=testfile.txt&type=',
+      );
+
+      final attachment = EmailUtils.parsingAttachmentByUri(uri);
+
+      expect(attachment, isNotNull);
+      expect(attachment!.blobId?.value, 'blobId');
+      expect(attachment.name, 'testfile.txt');
+      expect(attachment.type, isNull);
+    });
+  });
+}