Improve #818 test a bit

Author: cowtowncoder

src/test/java/com/fasterxml/jackson/failing/Fuzz51806JsonPointerParseTest.java

@@ -4,24 +4,49 @@
 import com.fasterxml.jackson.core.JsonPointer;
 
 // For https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=51806
-// (via databind, but we don't need that)
+// (reported as [core#818]
 public class Fuzz51806JsonPointerParseTest extends BaseTest
 {
     // Before fix, looks like this is enough to cause StackOverflowError
     private final static int TOO_DEEP_PATH = 6000;
 
-    // Verify that very deep/long (by number of segments) JsonPointer
-    // may still be parsed ok
-    public void testJsonPointerParseTail() throws Exception
+    // Verify that a very deep/long (by number of segments) JsonPointer
+    // may still be parsed ok, for "simple" case (no quoted chars)
+    public void testJsonPointerParseTailSimple()
     {
-        JsonPointer p = JsonPointer.compile(_generatePath(TOO_DEEP_PATH));
+        _testJsonPointer(_generatePath(TOO_DEEP_PATH, false));
+    }
+
+    public void testJsonPointerParseTailWithQuoted()
+    {
+        _testJsonPointer(_generatePath(TOO_DEEP_PATH, true));
+    }
+
+    private void _testJsonPointer(String pathExpr)
+    {
+        JsonPointer p = JsonPointer.compile(pathExpr);
         assertNotNull(p);
+        // But also verify it didn't change
+        assertEquals(pathExpr, p.toString());
     }
 
-    private String _generatePath(int depth) {
+    private String _generatePath(int depth, boolean escaped) {
         StringBuilder sb = new StringBuilder(4 * depth);
         for (int i = 0; i < depth; ++i) {
-            sb.append("/a").append(depth);
+            sb.append('/')
+                .append((char) ('a' + i%25))
+                .append(i);
+
+            if (escaped) {
+                switch (i & 7) {
+                case 1:
+                    sb.append("~0x");
+                    break;
+                case 4:
+                    sb.append("~1y");
+                    break;
+                }
+            }
         }
         return sb.toString();
     }