common/testing/EqualsTesterTest.java

/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed 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 com.google.common.testing;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Sets;
import java.util.Set;
import junit.framework.AssertionFailedError;
import junit.framework.TestCase;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Unit tests for {@link EqualsTester}.
 *
 * @author Jim McMaster
 */
@GwtCompatible
@SuppressWarnings("MissingTestCall")
public class EqualsTesterTest extends TestCase {
  private ValidTestObject reference;
  private EqualsTester equalsTester;
  private ValidTestObject equalObject1;
  private ValidTestObject equalObject2;
  private ValidTestObject notEqualObject1;

  @Override
  public void setUp() throws Exception {
    super.setUp();
    reference = new ValidTestObject(1, 2);
    equalsTester = new EqualsTester();
    equalObject1 = new ValidTestObject(1, 2);
    equalObject2 = new ValidTestObject(1, 2);
    notEqualObject1 = new ValidTestObject(0, 2);
  }

  /** Test null reference yields error */
  public void testAddNullReference() {
    try {
      equalsTester.addEqualityGroup((Object) null);
      fail("Should fail on null reference");
    } catch (NullPointerException e) {
    }
  }

  /** Test equalObjects after adding multiple instances at once with a null */
  public void testAddTwoEqualObjectsAtOnceWithNull() {
    try {
      equalsTester.addEqualityGroup(reference, equalObject1, null);
      fail("Should fail on null equal object");
    } catch (NullPointerException e) {
    }
  }

  /** Test adding null equal object yields error */
  public void testAddNullEqualObject() {
    try {
      equalsTester.addEqualityGroup(reference, (Object[]) null);
      fail("Should fail on null equal object");
    } catch (NullPointerException e) {
    }
  }

  /**
   * Test adding objects only by addEqualityGroup, with no reference object specified in the
   * constructor.
   */
  public void testAddEqualObjectWithOArgConstructor() {
    equalsTester.addEqualityGroup(equalObject1, notEqualObject1);
    try {
      equalsTester.testEquals();
    } catch (AssertionFailedError e) {
      assertErrorMessage(
          e,
          equalObject1
              + " [group 1, item 1] must be Object#equals to "
              + notEqualObject1
              + " [group 1, item 2]");
      return;
    }
    fail("Should get not equal to equal object error");
  }

  /**
   * Test EqualsTester with no equals or not equals objects. This checks proper handling of null,
   * incompatible class and reflexive tests
   */
  public void testTestEqualsEmptyLists() {
    equalsTester.addEqualityGroup(reference);
    equalsTester.testEquals();
  }

  /**
   * Test EqualsTester after populating equalObjects. This checks proper handling of equality and
   * verifies hashCode for valid objects
   */
  public void testTestEqualsEqualsObjects() {
    equalsTester.addEqualityGroup(reference, equalObject1, equalObject2);
    equalsTester.testEquals();
  }

  /** Test proper handling of case where an object is not equal to itself */
  public void testNonReflexiveEquals() {
    Object obj = new NonReflexiveObject();
    equalsTester.addEqualityGroup(obj);
    try {
      equalsTester.testEquals();
    } catch (AssertionFailedError e) {
      assertErrorMessage(e, obj + " must be Object#equals to itself");
      return;
    }
    fail("Should get non-reflexive error");
  }

  /** Test proper handling where an object tests equal to null */
  public void testInvalidEqualsNull() {
    Object obj = new InvalidEqualsNullObject();
    equalsTester.addEqualityGroup(obj);
    try {
      equalsTester.testEquals();
    } catch (AssertionFailedError e) {
      assertErrorMessage(e, obj + " must not be Object#equals to null");
      return;
    }
    fail("Should get equal to null error");
  }

  /** Test proper handling where an object incorrectly tests for an incompatible class */
  public void testInvalidEqualsIncompatibleClass() {
    Object obj = new InvalidEqualsIncompatibleClassObject();
    equalsTester.addEqualityGroup(obj);
    try {
      equalsTester.testEquals();
    } catch (AssertionFailedError e) {
      assertErrorMessage(
          e, obj + " must not be Object#equals to an arbitrary object of another class");
      return;
    }
    fail("Should get equal to incompatible class error");
  }

  /** Test proper handling where an object is not equal to one the user has said should be equal */
  public void testInvalidNotEqualsEqualObject() {
    equalsTester.addEqualityGroup(reference, notEqualObject1);
    try {
      equalsTester.testEquals();
    } catch (AssertionFailedError e) {
      assertErrorMessage(e, reference + " [group 1, item 1]");
      assertErrorMessage(e, notEqualObject1 + " [group 1, item 2]");
      return;
    }
    fail("Should get not equal to equal object error");
  }

  /**
   * Test for an invalid hashCode method, i.e., one that returns different value for objects that
   * are equal according to the equals method
   */
  public void testInvalidHashCode() {
    Object a = new InvalidHashCodeObject(1, 2);
    Object b = new InvalidHashCodeObject(1, 2);
    equalsTester.addEqualityGroup(a, b);
    try {
      equalsTester.testEquals();
    } catch (AssertionFailedError e) {
      assertErrorMessage(
          e,
          "the Object#hashCode ("
              + a.hashCode()
              + ") of "
              + a
              + " [group 1, item 1] must be equal to the Object#hashCode ("
              + b.hashCode()
              + ") of "
              + b);
      return;
    }
    fail("Should get invalid hashCode error");
  }

  public void testNullEqualityGroup() {
    EqualsTester tester = new EqualsTester();
    try {
      tester.addEqualityGroup((Object[]) null);
      fail();
    } catch (NullPointerException e) {
    }
  }

  public void testNullObjectInEqualityGroup() {
    EqualsTester tester = new EqualsTester();
    try {
      tester.addEqualityGroup(1, null, 3);
      fail();
    } catch (NullPointerException e) {
      assertErrorMessage(e, "at index 1");
    }
  }

  public void testSymmetryBroken() {
    EqualsTester tester =
        new EqualsTester().addEqualityGroup(named("foo").addPeers("bar"), named("bar"));
    try {
      tester.testEquals();
    } catch (AssertionFailedError e) {
      assertErrorMessage(e, "bar [group 1, item 2] must be Object#equals to foo [group 1, item 1]");
      return;
    }
    fail("should failed because symmetry is broken");
  }

  public void testTransitivityBrokenInEqualityGroup() {
    EqualsTester tester =
        new EqualsTester()
            .addEqualityGroup(
                named("foo").addPeers("bar", "baz"),
                named("bar").addPeers("foo"),
                named("baz").addPeers("foo"));
    try {
      tester.testEquals();
    } catch (AssertionFailedError e) {
      assertErrorMessage(e, "bar [group 1, item 2] must be Object#equals to baz [group 1, item 3]");
      return;
    }
    fail("should failed because transitivity is broken");
  }

  public void testUnequalObjectsInEqualityGroup() {
    EqualsTester tester = new EqualsTester().addEqualityGroup(named("foo"), named("bar"));
    try {
      tester.testEquals();
    } catch (AssertionFailedError e) {
      assertErrorMessage(e, "foo [group 1, item 1] must be Object#equals to bar [group 1, item 2]");
      return;
    }
    fail("should failed because of unequal objects in the same equality group");
  }

  public void testTransitivityBrokenAcrossEqualityGroups() {
    EqualsTester tester =
        new EqualsTester()
            .addEqualityGroup(named("foo").addPeers("bar"), named("bar").addPeers("foo", "x"))
            .addEqualityGroup(named("baz").addPeers("x"), named("x").addPeers("baz", "bar"));
    try {
      tester.testEquals();
    } catch (AssertionFailedError e) {
      assertErrorMessage(
          e, "bar [group 1, item 2] must not be Object#equals to x [group 2, item 2]");
      return;
    }
    fail("should failed because transitivity is broken");
  }

  public void testEqualityGroups() {
    new EqualsTester()
        .addEqualityGroup(named("foo").addPeers("bar"), named("bar").addPeers("foo"))
        .addEqualityGroup(named("baz"), named("baz"))
        .testEquals();
  }

  public void testEqualityBasedOnToString() {
    try {
      new EqualsTester().addEqualityGroup(new EqualsBasedOnToString("foo")).testEquals();
      fail();
    } catch (AssertionFailedError e) {
      assertTrue(e.getMessage().contains("toString representation"));
    }
  }

  private static void assertErrorMessage(Throwable e, String message) {
    // TODO(kevinb): use a Truth assertion here
    if (!e.getMessage().contains(message)) {
      fail("expected <" + e.getMessage() + "> to contain <" + message + ">");
    }
  }

  /**
   * Test class with valid equals and hashCode methods. Testers created with instances of this class
   * should always pass.
   */
  private static class ValidTestObject {
    private int aspect1;
    private int aspect2;

    ValidTestObject(int aspect1, int aspect2) {
      this.aspect1 = aspect1;
      this.aspect2 = aspect2;
    }

    @Override
    public boolean equals(@Nullable Object o) {
      if (!(o instanceof ValidTestObject)) {
        return false;
      }
      ValidTestObject other = (ValidTestObject) o;
      if (aspect1 != other.aspect1) {
        return false;
      }
      if (aspect2 != other.aspect2) {
        return false;
      }
      return true;
    }

    @Override
    public int hashCode() {
      int result = 17;
      result = 37 * result + aspect1;
      result = 37 * result + aspect2;
      return result;
    }
  }

  /** Test class with invalid hashCode method. */
  private static class InvalidHashCodeObject {
    private int aspect1;
    private int aspect2;

    InvalidHashCodeObject(int aspect1, int aspect2) {
      this.aspect1 = aspect1;
      this.aspect2 = aspect2;
    }

    @SuppressWarnings("EqualsHashCode")
    @Override
    public boolean equals(@Nullable Object o) {
      if (!(o instanceof InvalidHashCodeObject)) {
        return false;
      }
      InvalidHashCodeObject other = (InvalidHashCodeObject) o;
      if (aspect1 != other.aspect1) {
        return false;
      }
      if (aspect2 != other.aspect2) {
        return false;
      }
      return true;
    }
  }

  /** Test class that violates reflexivity. It is not equal to itself */
  private static class NonReflexiveObject {

    @Override
    public boolean equals(@Nullable Object o) {
      return false;
    }

    @Override
    public int hashCode() {
      return super.hashCode();
    }
  }

  /** Test class that returns true if the test object is null */
  private static class InvalidEqualsNullObject {

    @Override
    public boolean equals(@Nullable Object o) {
      return o == this || o == null;
    }

    @Override
    public int hashCode() {
      return 0;
    }
  }

  /** Test class that returns true even if the test object is of the wrong class */
  private static class InvalidEqualsIncompatibleClassObject {

    @Override
    public boolean equals(@Nullable Object o) {
      return o != null;
    }

    @Override
    public int hashCode() {
      return 0;
    }
  }

  private static NamedObject named(String name) {
    return new NamedObject(name);
  }

  private static class NamedObject {
    private final Set<String> peerNames = Sets.newHashSet();

    private final String name;

    NamedObject(String name) {
      this.name = Preconditions.checkNotNull(name);
    }

    NamedObject addPeers(String... names) {
      peerNames.addAll(ImmutableList.copyOf(names));
      return this;
    }

    @Override
    public boolean equals(@Nullable Object obj) {
      if (obj instanceof NamedObject) {
        NamedObject that = (NamedObject) obj;
        return name.equals(that.name) || peerNames.contains(that.name);
      }
      return false;
    }

    @Override
    public int hashCode() {
      return 0;
    }

    @Override
    public String toString() {
      return name;
    }
  }

  private static final class EqualsBasedOnToString {
    private final String s;

    private EqualsBasedOnToString(String s) {
      this.s = s;
    }

    @Override
    public boolean equals(@Nullable Object obj) {
      return obj != null && obj.toString().equals(toString());
    }

    @Override
    public int hashCode() {
      return s.hashCode();
    }

    @Override
    public String toString() {
      return s;
    }
  }
}