Add comprehensive cross-platform compatibility integration test

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

src/test/java/org/casbin/jcasbin/main/EvalCrossPlatformTest.java

diff --git a/src/test/java/org/casbin/jcasbin/main/EvalCrossPlatformTest.java b/src/test/java/org/casbin/jcasbin/main/EvalCrossPlatformTest.java
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+// Copyright 2024 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.
+
+package org.casbin.jcasbin.main;
+
+import org.casbin.jcasbin.util.ExpressionEvaluator;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+/**
+ * Integration test to demonstrate the fix for the eval() function issue.
+ * This test validates that the expression evaluator prevents the use of
+ * aviatorscript-specific syntax mentioned in the issue, ensuring
+ * cross-platform compatibility.
+ */
+public class EvalCrossPlatformTest {
+
+    /**
+     * Test that aviatorscript-specific syntax mentioned in the issue is blocked.
+     * Issue mentioned: seq.list(), string.startsWith(), string.endsWith(), include(seq.list(),xx)
+     */
+    @Test
+    public void testAviatorScriptSyntaxFromIssue_IsBlocked() {
+        // All these expressions from the issue description should be blocked
+        
+        // 1. seq.list() syntax
+        try {
+            ExpressionEvaluator.validateExpression("seq.list('A', 'B')");
+            fail("seq.list() should be blocked");
+        } catch (IllegalArgumentException e) {
+            assertTrue("Should mention non-standard operations", 
+                e.getMessage().contains("non-standard Casbin operations"));
+        }
+        
+        // 2. string.startsWith() syntax
+        try {
+            ExpressionEvaluator.validateExpression("string.startsWith(r.obj, '/data')");
+            fail("string.startsWith() should be blocked");
+        } catch (IllegalArgumentException e) {
+            assertTrue("Should mention non-standard operations", 
+                e.getMessage().contains("non-standard Casbin operations"));
+        }
+        
+        // 3. string.endsWith() syntax
+        try {
+            ExpressionEvaluator.validateExpression("string.endsWith(r.obj, '.txt')");
+            fail("string.endsWith() should be blocked");
+        } catch (IllegalArgumentException e) {
+            assertTrue("Should mention non-standard operations", 
+                e.getMessage().contains("non-standard Casbin operations"));
+        }
+        
+        // 4. include(seq.list(),xx) syntax
+        try {
+            ExpressionEvaluator.validateExpression("include(seq.list('admin', 'user'), r.sub.role)");
+            fail("include(seq.list(),xx) should be blocked");
+        } catch (IllegalArgumentException e) {
+            assertTrue("Should mention non-standard operations", 
+                e.getMessage().contains("non-standard Casbin operations"));
+        }
+    }
+
+    /**
+     * Test that standard Casbin expressions work correctly.
+     * These should be portable across all Casbin implementations.
+     */
+    @Test
+    public void testStandardCasbinExpressions_AreAllowed() {
+        // All these standard expressions should work
+        String[] standardExpressions = {
+            // Property access
+            "r.sub.name == 'alice'",
+            "r.sub.age > 18",
+            "r.obj == '/data1'",
+            "r.act == 'read'",
+            
+            // Logical operators
+            "r.sub.age > 18 && r.sub.age < 60",
+            "r.sub.name == 'alice' || r.sub.name == 'bob'",
+            "!(r.sub.blocked == true)",
+            
+            // Comparison operators
+            "r.sub.level >= 5",
+            "r.sub.score != 0",
+            "r.domain == 'domain1'",
+            
+            // Arithmetic operations
+            "r.sub.age + 10 > 28",
+            "r.sub.count * 2 <= 100",
+            
+            // Registered functions (these are part of standard Casbin)
+            "keyMatch(r.obj, '/api/*')",
+            "regexMatch(r.obj, '^/data[0-9]+$')",
+            "custom(r.obj)"
+        };
+        
+        for (String expr : standardExpressions) {
+            try {
+                ExpressionEvaluator.validateExpression(expr);
+                // Success - standard expression is allowed
+            } catch (IllegalArgumentException e) {
+                fail("Standard expression should be allowed: " + expr + " - Error: " + e.getMessage());
+            }
+        }
+    }
+
+    /**
+     * Test that the solution achieves cross-platform compatibility.
+     * The same expressions should work identically on Go, Node.js, Python, etc.
+     */
+    @Test
+    public void testCrossPlatformCompatibility() {
+        // These expressions use only standard operators that are available
+        // in all Casbin implementations
+        
+        String[] crossPlatformExpressions = {
+            // Instead of seq.list('A', 'B'), use standard comparisons:
+            "r.sub.role == 'admin' || r.sub.role == 'moderator'",
+            
+            // Instead of string.startsWith(), use keyMatch or regexMatch:
+            "keyMatch(r.obj, '/api/*')",
+            "regexMatch(r.obj, '^/api/')",
+            
+            // Instead of string.endsWith(), use regexMatch:
+            "regexMatch(r.obj, '\\\\.txt$')",
+            
+            // Instead of include(seq.list(),xx), use logical OR:
+            "r.sub.dept == 'engineering' || r.sub.dept == 'sales'"
+        };
+        
+        for (String expr : crossPlatformExpressions) {
+            try {
+                ExpressionEvaluator.validateExpression(expr);
+                // Success - cross-platform compatible expression
+            } catch (IllegalArgumentException e) {
+                fail("Cross-platform expression should be allowed: " + expr);
+            }
+        }
+    }
+
+    /**
+     * Test that security is improved by blocking operations beyond Casbin spec.
+     */
+    @Test
+    public void testSecurityImprovement_BlocksUnsafeOperations() {
+        // These operations go beyond Casbin specification and could be security risks
+        String[] unsafeOperations = {
+            "new java.io.File('/etc/passwd')",
+            "import java.lang.System",
+            "let x = System.getProperty('user.home')",
+            "fn hack() { return 'exploit' }",
+            "lambda(x) -> System.exit(0)",
+            "for (i = 0; i < 1000000; i++)",  // potential DoS
+            "while (true)",                    // infinite loop
+            "math.random()"                    // non-deterministic
+        };
+        
+        for (String expr : unsafeOperations) {
+            try {
+                ExpressionEvaluator.validateExpression(expr);
+                fail("Unsafe operation should be blocked: " + expr);
+            } catch (IllegalArgumentException e) {
+                // Success - unsafe operation is blocked
+                assertTrue("Should indicate non-standard operations", 
+                    e.getMessage().contains("non-standard Casbin operations"));
+            }
+        }
+    }
+}