Add test validating exact GitHub issue scenario

Co-authored-by: nomeguy <85475922+nomeguy@users.noreply.github.com>

Author: Copilot

test/github_issue_test.dart

@@ -0,0 +1,74 @@
+// Copyright 2018-2021 The Casbin Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+/// This test validates the exact scenario described in the GitHub issue
+/// to ensure the fix works as expected for the user's use case.
+
+import 'package:casbin/casbin.dart';
+import 'package:test/test.dart';
+import 'dart:convert';
+
+void main() {
+  test('GitHub issue scenario - ABAC with JSON should work exactly as described', () {
+    // Exact model from the GitHub issue
+    final model = Model()..loadModelFromText('''
+[request_definition]
+r = sub, obj, act
+
+[policy_definition]
+p = sub, obj, act, condition
+
+[policy_effect]
+e = some(where (p.eft == allow))
+
+[matchers]
+m = eval(p.condition) && r.obj == p.obj && r.act == p.act
+''');
+
+    final enforcer = Enforcer.initWithModelAndAdapter(model);
+    
+    // Exact policy from the GitHub issue
+    final policyLine = 'p, {"age": 18}, /data1, read, r.sub.age >= 18 && r.sub.age < 60';
+    final parts = policyLine.split(',').map((e) => e.trim()).toList();
+    
+    // Remove the 'p' prefix and add the policy
+    enforcer.addPolicy([parts[1], parts[2], parts[3], parts[4]]);
+    
+    // Test with age 25 (should be allowed)
+    String subJson = jsonEncode({"age": 25});
+    bool result = enforcer.enforce([subJson, '/data1', 'read']);
+    
+    expect(result, isTrue, reason: 'Age 25 should be allowed (18 <= 25 < 60)');
+    
+    // Test with age 18 (boundary, should be allowed)
+    subJson = jsonEncode({"age": 18});
+    result = enforcer.enforce([subJson, '/data1', 'read']);
+    expect(result, isTrue, reason: 'Age 18 should be allowed (boundary condition)');
+    
+    // Test with age 17 (should be denied)
+    subJson = jsonEncode({"age": 17});
+    result = enforcer.enforce([subJson, '/data1', 'read']);
+    expect(result, isFalse, reason: 'Age 17 should be denied (< 18)');
+    
+    // Test with age 60 (should be denied)
+    subJson = jsonEncode({"age": 60});
+    result = enforcer.enforce([subJson, '/data1', 'read']);
+    expect(result, isFalse, reason: 'Age 60 should be denied (>= 60)');
+    
+    // Test with age 59 (boundary, should be allowed)
+    subJson = jsonEncode({"age": 59});
+    result = enforcer.enforce([subJson, '/data1', 'read']);
+    expect(result, isTrue, reason: 'Age 59 should be allowed (18 <= 59 < 60)');
+  });
+}