Add regression test for exception interop

Author: msimacek

graalpython/com.oracle.graal.python.test/src/com/oracle/graal/python/test/interop/InteropLibraryTest.java

@@ -40,24 +40,27 @@
  */
 package com.oracle.graal.python.test.interop;
 
-import org.junit.After;
-import org.junit.Before;
-import org.junit.Test;
-import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.List;
 
 import org.graalvm.polyglot.Context;
 import org.graalvm.polyglot.Context.Builder;
+import org.graalvm.polyglot.PolyglotException;
 import org.graalvm.polyglot.Value;
 import org.graalvm.polyglot.proxy.ProxyArray;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
 
 import com.oracle.graal.python.test.PythonTests;
 
-import java.util.Arrays;
-import java.util.Iterator;
-import java.util.List;
-
 public class InteropLibraryTest extends PythonTests {
     private Context context;
 
@@ -165,6 +168,24 @@ public void testForItemInLazyArray() {
         assertEquals(list.size() * 3, tripples.getArraySize());
     }
 
+    @Test
+    public void testException() {
+        try {
+            context.eval("python", "1/0");
+        } catch (PolyglotException e) {
+            Value exception = e.getGuestObject();
+            assertTrue(exception.hasMember("args"));
+            Value args = exception.getMember("args");
+            assertTrue(args.hasArrayElements());
+            assertEquals(1, args.getArraySize());
+            assertEquals("division by zero", args.getArrayElement(0).asString());
+            // This excercises isIdenticalOrUndefined message internally
+            assertNotEquals(exception, args);
+            return;
+        }
+        fail("didn't throw exception");
+    }
+
     private static final class LazyArray implements ProxyArray {
 
         private final Iterator<?> it;