How do I assert equality on two classes without an equals method

Question

Say I have a class with no equals   method  to which do not have the source   I want to assert equality on two instances of that class   I can do multiple asserts   assertEquals obj1 getFieldA    obj2 getFieldA     assertEquals obj1 getFieldB    obj2 getFieldB     assertEquals obj1 getFieldC    obj2 getFieldC           I don t like this solution because I don t get the full equality picture if an early assert fails   I can manually compare on my own and track the result   String errorStr       if  obj1 getFieldA   equals obj2 getFieldA           errorStr     expected      obj1 getFieldA        actual      obj2 getFieldA       n     if  obj1 getFieldB   equals obj2 getFieldB           errorStr     expected      obj1 getFieldB        actual      obj2 getFieldB       n         assertEquals     errorStr     This gives me the full equality picture  but is clunky  and I haven t even accounted for possible null problems    A third option is to use Comparator  but compareTo   will not tell me which fields failed equality   Is there a better practice to get what I want from the object  without subclassing and overridding equals  ugh

User · Answer

You can override the equals method of the class like:

@Override
public int hashCode() {
    int hash = 0;
    hash += (app != null ? app.hashCode() : 0);
    return hash;
}

@Override
public boolean equals(Object object) {
    HubRule other = (HubRule) object;

    if (this.app.equals(other.app)) {
        boolean operatorHubList = false;

        if (other.operator != null ? this.operator != null ? this.operator
                .equals(other.operator) : false : true) {
            operatorHubList = true;
        }

        if (operatorHubList) {
            return true;
        } else {
            return false;
        }
    } else {
        return false;
    }
}

Well, if you want to compare two object from a class you must implement in some way the equals and the hash code method

User · Answer

AssertJ assertions can be used to compare the values without  equals method properly overridden  e g    import static org assertj core api Assertions assertThat            assertThat actual       usingRecursiveComparison        isEqualTo expected

User · Answer

I stumbled on a very similar case   I wanted to compare on a test that an object had the same attribute values as another one  but methods like is    refEq    etc wouldn t work for reasons like my object having a null value in its id attribute   So this was the solution I found  well  a coworker found    import static org apache commons lang builder CompareToBuilder reflectionCompare   assertThat reflectionCompare expectedObject  actualObject  new String    fields   to   be   excluded     is 0      If the value obtained from reflectionCompare is 0  it means they are equal  If it is -1 or 1  they differ on some attribute

User · Answer

This is a generic compare method   that compares two objects of a same class for its values of it fields keep in mind those are accessible by get method   public static  lt T gt  void compare T a  T b  throws NoSuchMethodException  InvocationTargetException  IllegalAccessException       AssertionError error   null      Class A   a getClass        Class B   a getClass        for  Method mA   A getDeclaredMethods              if  mA getName   startsWith  get                  Method mB   B getMethod mA getName   null                try                   Assert assertEquals  Not Matched     mA invoke a  mB invoke b                 catch  AssertionError e                   if error  null                       error   new AssertionError e                                     else                       error addSuppressed e                                                       if error  null           throw error

User · Answer

You can use reflection to  automate  the full equality testing   you can implement the equality  tracking  code you wrote for a single field  then use reflection to run that test on all fields in the object

User · Answer

If you re using hamcrest for your asserts  assertThat  and don t want to pull in additional test libs  then you can use SamePropertyValuesAs samePropertyValuesAs to assert items that don t have an overridden equals method    The upside is that you don t have to pull in yet another test framework and it ll give a useful error when the assert fails  expected  field  lt value gt  but was field  lt something else gt   instead of expected  true but was false if you use something like EqualsBuilder reflectionEquals     The downside is that it is a shallow compare and there s no option for excluding fields  like there is in EqualsBuilder   so you ll have to work around nested objects  e g  remove them and compare them independently    Best Case   import static org hamcrest beans SamePropertyValuesAs samePropertyValuesAs      assertThat actual  is samePropertyValuesAs expected       Ugly Case   import static org hamcrest beans SamePropertyValuesAs samePropertyValuesAs      SomeClass expected   buildExpected     SomeClass actual   sut doSomething     assertThat actual getSubObject    is samePropertyValuesAs expected getSubObject           expected setSubObject null   actual setSubObject null    assertThat actual  is samePropertyValuesAs expected       So  pick your poison  Additional framework  e g  Unitils   unhelpful error  e g  EqualsBuilder   or shallow compare  hamcrest

User · Answer

Can you put the comparision code you posted into some static utility method   public static String findDifference Type obj1  Type obj2        String difference           if  obj1 getFieldA      null  amp  amp  obj2 getFieldA      null                 obj1 getFieldA   equals obj2 getFieldA               difference     Difference at field A      obj1 -                     obj1 getFieldA        obj2 -     obj2 getFieldA              if  obj1 getFieldB      null  amp  amp  obj2 getFieldB      null                 obj1 getFieldB   equals obj2 getFieldB               difference     Difference at field B      obj1 -                     obj1 getFieldB        obj2 -     obj2 getFieldB                               return difference      Than you can use this method in JUnit like this   assertEquals  Objects aren t equal       findDifferences obj1  obj     which isn t clunky and gives you full information about differences  if they exist  through not exactly in normal form of assertEqual but you get all the info so it should be good

User · Answer

From your comments to other answers  I don t understand what you want   Just for the sake of discussion  lets say that the the class did override the equals method   So your UT will look something like   SomeType expected      bla SomeType actual      bli  Assert assertEquals expected  actual      And you are done  Moreover  you can not get the  full equality picture  if the assertion fails    From what I understand  you are saying that even if the type did override equals  you would not be interested in it  since you want to get the  full equality picture   So there is no point in extending and overriding equals either    So you have to options  either compare property by property  using reflection or hard-coded checks  I would suggest the latter  Or  compare human readable representations of these objects   For example  you can create a helper class that serializes the type you wish tocompare to an XML document and than compare the resulting XML  in this case  you can visually see what exactly is equal and what is not    This approach will give you the opportunity to look at the full picture but it is also relatively cumbersome  and a little error prone at first

User · Answer

You can use Apache commons lang ReflectionToStringBuilder  You can either specify the attributes you want to test one by one  or better  exclude those you don t want   String s   new ReflectionToStringBuilder o  ToStringStyle SHORT PREFIX STYLE                   setExcludeFieldNames new String      foo    bar     toString     You then compare the two strings as normal  For the point about reflection being slow  I assume this is only for testing  so shouldn t be so important

User · Answer

Compare field-by-field   assertNotNull  Object 1 is null   obj1   assertNotNull  Object 2 is null   obj2   assertEquals  Field A differs   obj1 getFieldA    obj2 getFieldA     assertEquals  Field B differs   obj1 getFieldB    obj2 getFieldB         assertEquals  Objects are not equal    obj1  obj2

User · Answer

I tried all the answers and nothing really worked for me    So I ve created my own method that compares simple java objects without going deep into nested structures      Method returns null if all fields match or string containing mismatch details    Only properties that have a getter method are compared   How to use          assertNull TestUtils diff obj1 obj2 ignore field1  ignore field2      Sample output if there is a mismatch  Output shows property names and respective values of compared objects  alert id 1 2   city Moscow London    Code  Java 8 and above     public static String diff Object x1  Object x2  String     ignored  throws Exception          final StringBuilder response   new StringBuilder            for  Method m Arrays stream x1 getClass   getMethods    filter m- gt m getName   startsWith  get            amp  amp  m getParameterCount    0  collect toList                   final String field   m getName   substring 3  toLowerCase                if  Arrays stream ignored  map x- gt x toLowerCase    noneMatch ignoredField- gt ignoredField equals field                     Object v1   m invoke x1                   Object v2   m invoke x2                   if    v1  null  amp  amp   v1 equals v2       v2  null  amp  amp   v2 equals v1                         response append field  append      append v1  append      append v2  append      append                                                          return response length    0 null response substring 0 response length  -2

User · Answer

This won t help the OP  but it might help any C  developers who end up here     Like Enrique posted  you should override the equals method      Is there a better practice to get what I want from the object  without subclassing and overridding equals  ugh     My suggestion is to not use a subclass  Use a partial class   Partial Class Definitions  MSDN   So your class would look like     public partial class TheClass       public override bool Equals Object obj                   your implementation here           For Java  I would agree with the suggestion to use reflection  Just remember that you should avoid using reflection whenever possible  It is slow  hard to debug  and even harder to maintain into the future because IDEs could break your code by doing a field rename or something like that  Be careful

User · Answer

Mockito offers a reflection-matcher   For latest version of Mockito use   Assert assertTrue new ReflectionEquals expected  excludeFields  matches actual      For older versions use   Assert assertThat actual  new ReflectionEquals expected  excludeFields

User · Answer

In common case with AssertJ you can create custom comparator strategy   assertThat frodo  usingComparator raceComparator  isEqualTo sam  assertThat fellowshipOfTheRing  usingElementComparator raceComparator  contains sauron      Using a custom comparison strategy in assertions  AssertJ examples

User · Answer

I had the exact same conundrum when unit testing an Android app  and the easiest solution I came up with was simply to use Gson to convert my actual and expected value objects into json and compare them as strings    String actual   new Gson   toJson  myObj getValues      String expected   new Gson   toJson  new MyValues true 1      assertEquals expected  actual     The advantages of this over manually comparing field-by-field is that you compare all your fields  so even if you later on add a new field to your class it will get automatically tested  as compared to if you were using a bunch of assertEquals   on all the fields  which would then need to be updated if you add more fields to your class   jUnit also displays the strings for you so you can directly see where they differ  Not sure how reliable the field ordering by Gson is though  that could be a potential problem

User · Answer

The library Hamcrest 1 3 Utility Matchers has a special matcher that uses reflection instead of equals   assertThat obj1  reflectEquals obj2

User · Answer

I know it s a bit old  but I hope it helps   I run into the same problem that you  so  after investigation  I found few similar questions than this one  and  after finding the solution  I m answering the same in those  since I thought it could to help others   The most voted answer  not the one picked by the author  of this similar question  is the most suitable solution for you   Basically  it consist on using the library called Unitils   This is the use   User user1   new User 1   John    Doe    User user2   new User 1   John    Doe    assertReflectionEquals user1  user2     Which will pass even if the class User doesn t implement equals    You can see more examples and a really cool assert called assertLenientEquals in their tutorial

User · Answer

Since this question is old  I will suggest another modern approach using JUnit 5       I don t like this solution because I don t get the full equality picture if an early assert fails    With JUnit 5  there is a method called Assertions assertAll   which will allow you to group all assertions in your test together and it will execute each one and output any failed assertions at the end  This means that any assertions that fail first will not stop the execution of latter assertions   assertAll  Test obj1 with obj2 equality          - gt  assertEquals obj1 getFieldA    obj2 getFieldA            - gt  assertEquals obj1 getFieldB    obj2 getFieldB            - gt  assertEquals obj1 getFieldC    obj2 getFieldC

User · Answer

As an alternative for junit-only  you can set fields to null prior to equals assertion       actual setCreatedDate null      excludes date assertion     expected setCreatedDate null        assertEquals expected  actual

User · Answer

Using Shazamcrest  you can do   assertThat obj1  sameBeanAs obj2

User · Answer

Some of the reflection compare methods are shallow  Another option is to convert the object to a json  and compare the strings   import com fasterxml jackson core JsonProcessingException  import com fasterxml jackson databind ObjectMapper      public static String getJsonString Object obj     try       ObjectMapper objectMapper   new ObjectMapper        return bjectMapper writerWithDefaultPrettyPrinter   writeValueAsString obj          catch  JsonProcessingException e            LOGGER error  Error parsing log entry   e           return null              assertEquals getJsonString MyexpectedObject   getJsonString MyActualObject

User · Answer

There is many correct answers here  but I would like to add my version too  This is based on Assertj   import static org assertj core api Assertions assertThat   public class TestClass        public void test                do the actual test         assertThat actualObject               isEqualToComparingFieldByFieldRecursively expectedObject             UPDATE  In assertj v3 13 2 this method is deprecated as pointed out by Woodz in comment  Current recommendation is  public class TestClass        public void test                do the actual test         assertThat actualObject               usingRecursiveComparison                isEqualTo expectedObject

User · Answer

I generally implement this usecase using org apache commons lang3 builder EqualsBuilder  Assert assertTrue EqualsBuilder reflectionEquals expected actual

[java] How do I assert equality on two classes without an equals method?

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