[COMPRESS-872] Add MultiKeyMapCompress672Test

src/test/java/org/apache/commons/collections4/map/MultiKeyMapCompress672Test.java

@@ -0,0 +1,100 @@
+/*
+ * 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.collections4.map;
+
+import java.util.Objects;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests COMPRESS-872
+ * <p>
+ * Claim:
+ * </p>
+ * <ol>
+ * <li>Create a MultiKeyMap, with key(s) of a type (class/record) which has some fields.
+ * <li>Use multiKeyMap.put(T... keys, V value), to create an entry in the Map, to map the keys to a value
+ * <li>Use multiKeyMap.get(T... keys), to verify that the mapping exists and returns the expected value.
+ * <li>Modify/alter any of the objects used as a key. It is enough to change the value of any member field of any of the objects.
+ * <li>Use multiKeyMap.get(T... keys) again, however, now there is no mapping for these keys!
+ * <li>Use multiKeyMap.get(T... keys) with the new modified/altered objects, and it will return the expected value
+ * </ol>
+ * COUNTER CLAIM: The class is documented to use MultiKey which documents key elements as "The keys should be immutable".
+ */
+public class MultiKeyMapCompress672Test {
+
+    private static final class KeyFixture {
+
+        private String value = "originalValue";
+
+        @Override
+        public boolean equals(final Object obj) {
+            if (obj == null) {
+                return false;
+            }
+            if (obj.getClass() != this.getClass()) {
+                return false;
+            }
+            if (this == obj) {
+                return true;
+            }
+            final KeyFixture object = (KeyFixture) obj;
+            if (getValue() == null) {
+                return object.getValue() == null;
+            }
+            return getValue().equals(object.getValue());
+        }
+
+        public String getValue() {
+            return value;
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hashCode(value);
+        }
+
+        public void setValue(final String field) {
+            this.value = field;
+        }
+    }
+
+    private static final String KEY_1 = "key1";
+
+    private final MultiKeyMap<Object, String> multiKeyMap = new MultiKeyMap<>();
+
+    @Test
+    public void testMutateKey() {
+        // Both objects have the 'field' value set to "originalValue"
+        final KeyFixture keyFixture2Ro = new KeyFixture();
+        final KeyFixture keyFixture2Rw = new KeyFixture();
+        // Put original mapping
+        Assertions.assertNull(multiKeyMap.put(KEY_1, keyFixture2Rw, "value"));
+        // Both mappings are correct
+        Assertions.assertEquals("value", multiKeyMap.get(KEY_1, keyFixture2Rw));
+        Assertions.assertEquals("value", multiKeyMap.get(KEY_1, keyFixture2Ro));
+        // Modify 'fixture2'
+        keyFixture2Rw.setValue("newValue");
+        // Modified mapping SHOULD NOT work
+        Assertions.assertNull(multiKeyMap.get(KEY_1, keyFixture2Rw));
+        // Claim: Original mapping SHOULD work
+        // COUNTER CLAIM: The class is documented to use MultiKey which documents key elements as "The keys should be immutable".
+        Assertions.assertNotEquals("value", multiKeyMap.get(KEY_1, keyFixture2Ro));
+    }
+}