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Elasticsearch subproject :test:framework
There is a newer version: 8.16.0
/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0 and the Server Side Public License, v 1; you may not use this file except
 * in compliance with, at your election, the Elastic License 2.0 or the Server
 * Side Public License, v 1.
 */

package org.elasticsearch.test;

import org.elasticsearch.core.Releasable;

import java.io.IOException;
import java.util.function.Consumer;

import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.not;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertThat;
import static org.junit.Assert.assertTrue;

/**
 * Utility class that encapsulates standard checks and assertions around testing the equals() and hashCode()
 * methods of objects that implement them.
 */
public class EqualsHashCodeTestUtils {

    private static Object[] someObjects = new Object[] { "some string", Integer.valueOf(1), Double.valueOf(1.0) };

    /**
     * A function that makes a copy of its input argument
     */
    public interface CopyFunction {
        T copy(T t) throws IOException;
    }

    /**
     * A function that creates a copy of its input argument that is different from its
     * input in exactly one aspect (e.g. one parameter of a class instance should change)
     */
    public interface MutateFunction {
        T mutate(T t) throws IOException;
    }

    /**
     * Perform common equality and hashCode checks on the input object
     * @param original the object under test
     * @param copyFunction a function that creates a deep copy of the input object
     */
    public static  void checkEqualsAndHashCode(T original, CopyFunction copyFunction) {
        checkEqualsAndHashCode(original, copyFunction, null);
    }

    /**
     * Perform common equality and hashCode checks on the input object
     * @param original the object under test
     * @param copyFunction a function that creates a deep copy of the input object
     * @param mutationFunction a function that creates a copy of the input object that is different
     * from the input in one aspect. The output of this call is used to check that it is not equal()
     * to the input object
     */
    public static  void checkEqualsAndHashCode(T original, CopyFunction copyFunction, MutateFunction mutationFunction) {
        checkEqualsAndHashCode(original, copyFunction, mutationFunction, unused -> {});
    }

    /**
     * Perform common equality and hashCode checks on the input object
     * @param original the object under test
     * @param copyFunction a function that creates a deep copy of the input object
     * @param mutationFunction a function that creates a copy of the input object that is different
     * @param dispose dispose of the copy, usually {@link Releasable#close} or a noop
     * from the input in one aspect. The output of this call is used to check that it is not equal()
     * to the input object
     */
    public static  void checkEqualsAndHashCode(
        T original,
        CopyFunction copyFunction,
        MutateFunction mutationFunction,
        Consumer dispose
    ) {
        try {
            String objectName = original.getClass().getSimpleName();
            assertFalse(objectName + " is equal to null", original.equals(null));
            // TODO not sure how useful the following test is
            assertFalse(objectName + " is equal to incompatible type", original.equals(ESTestCase.randomFrom(someObjects)));
            assertTrue(objectName + " is not equal to self", original.equals(original));
            assertThat(
                objectName + " hashcode returns different values if called multiple times",
                original.hashCode(),
                equalTo(original.hashCode())
            );
            if (mutationFunction != null) {
                T mutation = mutationFunction.mutate(original);
                try {
                    assertThat(objectName + " mutation should not be equal to original", mutation, not(equalTo(original)));
                    // equals is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only
                    // if y.equals(x) returns true. Conversely, y.equals(x) should return true if and only if x.equals(y)
                    assertThat("original should not be equal to mutation" + objectName, original, not(equalTo(mutation)));
                } finally {
                    dispose.accept(mutation);
                }
            }

            T copy = copyFunction.copy(original);
            try {
                assertTrue(objectName + " copy is not equal to self", copy.equals(copy));
                assertThat(objectName + " is not equal to its copy", original, equalTo(copy));
                assertTrue("equals is not symmetric", copy.equals(original));
                assertThat(objectName + " hashcode is different from copies hashcode", copy.hashCode(), equalTo(original.hashCode()));

                T secondCopy = copyFunction.copy(copy);
                try {
                    assertTrue("second copy is not equal to self", secondCopy.equals(secondCopy));
                    assertTrue("copy is not equal to its second copy", copy.equals(secondCopy));
                    assertThat(
                        "second copy's hashcode is different from original hashcode",
                        copy.hashCode(),
                        equalTo(secondCopy.hashCode())
                    );
                    assertTrue("equals is not transitive", original.equals(secondCopy));
                    assertTrue("equals is not symmetric", secondCopy.equals(copy));
                    assertTrue("equals is not symmetric", secondCopy.equals(original));
                } finally {
                    dispose.accept(secondCopy);
                }
            } finally {
                dispose.accept(copy);
            }
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}