1 files changed, 108 insertions, 0 deletions
diff --git a/src/test/java/org/apache/commons/lang3/builder/ReflectionToStringBuilderMutateInspectConcurrencyTest.java b/src/test/java/org/apache/commons/lang3/builder/ReflectionToStringBuilderMutateInspectConcurrencyTest.java
new file mode 100644
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+++ b/src/test/java/org/apache/commons/lang3/builder/ReflectionToStringBuilderMutateInspectConcurrencyTest.java
@@ -0,0 +1,108 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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.apache.commons.lang3.builder;
+
+import java.util.LinkedList;
+import java.util.Random;
+
+import org.apache.commons.lang3.AbstractLangTest;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests concurrent access for {@link ReflectionToStringBuilder}.
+ * <p>
+ * The {@link ToStringStyle} class includes a registry to avoid infinite loops for objects with circular references. We
+ * want to make sure that we do not get concurrency exceptions accessing this registry.
+ * </p>
+ *
+ * @see <a href="https://issues.apache.org/jira/browse/LANG-762">[LANG-762] Handle or document ReflectionToStringBuilder
+ *      and ToStringBuilder for collections that are not thread safe</a>
+ * @since 3.1
+ */
+public class ReflectionToStringBuilderMutateInspectConcurrencyTest extends AbstractLangTest {
+
+    class TestFixture {
+        private final LinkedList<Integer> listField = new LinkedList<>();
+        private final Random random = new Random();
+        private final int N = 100;
+
+        TestFixture() {
+            synchronized (this) {
+                for (int i = 0; i < N; i++) {
+                    listField.add(Integer.valueOf(i));
+                }
+            }
+        }
+
+        public synchronized void add() {
+            listField.add(Integer.valueOf(random.nextInt(N)));
+        }
+
+        public synchronized void delete() {
+            listField.remove(Integer.valueOf(random.nextInt(N)));
+        }
+    }
+
+    class MutatingClient implements Runnable {
+        private final TestFixture testFixture;
+        private final Random random = new Random();
+
+        MutatingClient(final TestFixture testFixture) {
+            this.testFixture = testFixture;
+        }
+
+        @Override
+        public void run() {
+            if (random.nextBoolean()) {
+                testFixture.add();
+            } else {
+                testFixture.delete();
+            }
+        }
+    }
+
+    class InspectingClient implements Runnable {
+        private final TestFixture testFixture;
+
+        InspectingClient(final TestFixture testFixture) {
+            this.testFixture = testFixture;
+        }
+
+        @Override
+        public void run() {
+            ReflectionToStringBuilder.toString(testFixture);
+        }
+    }
+
+    @Test
+    @Disabled
+    public void testConcurrency() {
+        final TestFixture testFixture = new TestFixture();
+        final int numMutators = 10;
+        final int numIterations = 10;
+        for (int i = 0; i < numIterations; i++) {
+            for (int j = 0; j < numMutators; j++) {
+                final Thread t = new Thread(new MutatingClient(testFixture));
+                t.start();
+                final Thread s = new Thread(new InspectingClient(testFixture));
+                s.start();
+            }
+        }
+    }
+}