Assert equals between 2 Lists in Junit

Question

How can I make an equality assertion between lists in a JUnit test case  Equality should be between the content of the list   For example   List lt String gt  numbers   Arrays asList  one    two    three    List lt String gt  numbers2   Arrays asList  one    two    three    List lt String gt  numbers3   Arrays asList  one    two    four         numbers should be equal to numbers2   numbers should not be equal to numbers3

User · Answer

You mentioned that you re interested in the equality of the contents of the list  and didn t mention order   So containsExactlyInAnyOrder from AssertJ is a good fit  It comes packaged with spring-boot-starter-test  for example  From the AssertJ docs ListAssert containsExactlyInAnyOrder   Verifies that the actual group contains exactly the given values and nothing else  in any order  Example       an Iterable is used in the example but it would also work with an array  Iterable lt Ring gt  elvesRings   newArrayList vilya  nenya  narya  vilya        assertion will pass  assertThat elvesRings  containsExactlyInAnyOrder vilya  vilya  nenya  narya        assertion will fail as vilya is contained twice in elvesRings   assertThat elvesRings  containsExactlyInAnyOrder nenya  vilya  narya

User · Answer

For JUnit 5 you can use assertIterableEquals   List lt String gt  numbers   Arrays asList  quot one quot    quot two quot    quot three quot    List lt String gt  numbers2   Arrays asList  quot one quot    quot two quot    quot three quot     Assertions assertIterableEquals numbers  numbers2    or assertArrayEquals and converting lists to arrays   List lt String gt  numbers   Arrays asList  quot one quot    quot two quot    quot three quot    List lt String gt  numbers2   Arrays asList  quot one quot    quot two quot    quot three quot    Assertions assertArrayEquals numbers toArray    numbers2 toArray

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List lt Integer gt  figureTypes   new ArrayList lt Integer gt                              Arrays asList                                   1                                   2                                  List lt Integer gt  figureTypes2   new ArrayList lt Integer gt                              Arrays asList                                   1                                   2     assertTrue figureTypes  equals figureTypes2

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You can use assertEquals in junit    import org junit Assert     import org junit Test        Test     public void test array pass                 List lt String gt  actual   Arrays asList  fee    fi    foe            List lt String gt  expected   Arrays asList  fee    fi    foe            Assert assertEquals actual expected           If the order of elements is different then it will return error      If you are asserting a model object list then you should   override the equals method in the specific model        Override     public boolean equals Object obj            if  obj    this                return true                    if  obj    null  amp  amp  obj instanceof ModelName                ModelName other    ModelName  obj              return this getItem   equals other getItem                        return false

User · Answer

assertEquals Object  Object  from JUnit4 JUnit 5 or   assertThat actual  is expected    from Hamcrest proposed in the other answers will work only as both equals   and toString   are overrided for the classes  and deeply  of the compared objects      It matters because the equality test in the assertion relies on equals   and the test failure message relies on toString   of the compared objects  For built-in classes such as String  Integer and so for     no problem as these override both equals   and toString    So it is perfectly valid to assert List lt String gt  or List lt Integer gt  with  assertEquals Object Object   And about this matter   you have to override equals   in a class because it makes sense in terms of object equality  not only to make assertions easier in a test with JUnit  To make assertions easier you have other ways  As a good practice I favor assertion matcher libraries      Here is a AssertJ solution     org assertj core api ListAssert containsExactly   is what you need   it verifies that the actual group contains exactly the given values and nothing else  in order as stated in the javadoc      Suppose a Foo class where you add elements and where you can get that  A unit test of Foo that asserts that the two lists have the same content could look like    import org assertj core api Assertions  import org junit jupiter api Test    Test void add   throws Exception       Foo foo   new Foo       foo add  One    Two    Three       Assertions assertThat foo getElements                  containsExactly  One    Two    Three        A AssertJ good point is that declaring a List as expected is needless   it makes the assertion straighter and the code more readable    Assertions assertThat foo getElements              containsExactly  One    Two    Three      But Assertion matcher libraries are a must because these will really further  Suppose now that Foo  doesn t store Strings but Bars instances  That is a very common need   With AssertJ the assertion is still simple to write  Better you can assert that the list content are equal even if the class of the elements doesn t override equals   hashCode   while JUnit way requires that    import org assertj core api Assertions  import static org assertj core groups Tuple tuple  import org junit jupiter api Test    Test void add   throws Exception       Foo foo   new Foo        foo add new Bar 1   One    new Bar 2   Two    new Bar 3   Three         Assertions assertThat foo getElements                   extracting Bar  getId  Bar  getName                 containsExactly tuple 1   One                                   tuple 2   Two                                   tuple 3   Three

User · Answer

I don t this the all the above answers are giving the exact solution for comparing two lists of Objects  Most of above approaches can be helpful in following limit of comparisons only - Size comparison - Reference comparison  But if we have same sized lists of objects and different data on the objects level then this comparison approaches won t help    I think the following approach will work perfectly with overriding equals and hashcode method on the user-defined object   I used Xstream lib for override equals and hashcode but we can override equals and hashcode by out won logics comparison too   Here is the example for your reference      import com thoughtworks xstream XStream       import java text ParseException      import java util ArrayList      import java util List       class TestClass         private String name        private String id         public void setName String value            this name   value                 public String getName             return this name                 public String getId             return id                 public void setId String id            this id   id                               see java lang Object equals java lang Object                   Override       public boolean equals Object o            XStream xstream   new XStream            String oxml   xstream toXML o           String myxml   xstream toXML this            return myxml equals oxml                                see java lang Object hashCode                    Override       public int hashCode             XStream xstream   new XStream            String myxml   xstream toXML this           return myxml hashCode                       public class XstreamCompareTest         public static void main String   args  throws ParseException         checkObjectEquals             private static void checkObjectEquals             List lt TestClass gt  testList1   new ArrayList lt TestClass gt             TestClass tObj1   new TestClass            tObj1 setId  test3            tObj1 setName  testname3            testList1 add tObj1            TestClass tObj2   new TestClass            tObj2 setId  test2            tObj2 setName  testname2            testList1 add tObj2            testList1 sort  TestClass t1  TestClass t2  - gt  t1 getId   compareTo t2 getId               List lt TestClass gt  testList2   new ArrayList lt TestClass gt             TestClass tObj3   new TestClass            tObj3 setId  test3            tObj3 setName  testname3            testList2 add tObj3            TestClass tObj4   new TestClass            tObj4 setId  test2            tObj4 setName  testname2            testList2 add tObj4            testList2 sort  TestClass t1  TestClass t2  - gt  t1 getId   compareTo t2 getId               if  isNotMatch testList1  testList2               System out println  The list are not matched              else             System out println  The list are matched                              private static boolean isNotMatch List lt TestClass gt  clist1  List lt TestClass gt  clist2            return clist1 size      clist2 size       clist1 equals clist2                   The most important thing is that you can ignore the fields by Annotation   XStreamOmitField  if you don t want to include any fields on the equal check of Objects  There are many Annotations like this to configure so have a look deep about the annotations of this lib   I am sure this answer will save your time to identify the correct approach for comparing two lists of objects     Please comment if you see any issues on this

User · Answer

assertEquals expected  result   works for me  Since this function gets two objects  you can pass anything to it   public static void assertEquals Object expected  Object actual        AssertEquals assertEquals expected  actual

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If you don t care about the order of the elements  I recommend ListAssert assertEquals in junit-addons   Link  http   junit-addons sourceforge net   For lazy Maven users        lt dependency gt           lt groupId gt junit-addons lt  groupId gt           lt artifactId gt junit-addons lt  artifactId gt           lt version gt 1 4 lt  version gt           lt scope gt test lt  scope gt       lt  dependency gt

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if you don t want to build up an array list   you can try this also    Test public void test array pass       List lt String gt  list   Arrays asList  fee    fi    foe      Strint listToString   list toString      Assert assertTrue listToString contains   fee  fi  foe           passes

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For junit4  This question deserves a new answer written for junit5  I realise this answer is written a couple years after the question  probably this feature wasn t around then  But now  it s easy to just do this   Test public void test array pass       List lt String gt  actual   Arrays asList  quot fee quot    quot fi quot    quot foe quot      List lt String gt  expected   Arrays asList  quot fee quot    quot fi quot    quot foe quot       assertThat actual  is expected      assertThat actual  is not expected        If you have a recent version of Junit installed with hamcrest  just add these imports  import static org junit Assert    import static org hamcrest CoreMatchers     http   junit org junit4 javadoc latest org junit Assert html assertThat T  org hamcrest Matcher  http   junit org junit4 javadoc latest org hamcrest CoreMatchers html http   junit org junit4 javadoc latest org hamcrest core Is html

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Don t reinvent the wheel   There s a Google Code library that does this for you  Hamcrest      Hamcrest  Provides a library of matcher objects  also known as constraints or predicates  allowing  match  rules to be defined declaratively  to be used in other frameworks  Typical scenarios include testing frameworks  mocking libraries and UI validation rules

User · Answer

Don t transform to string and compare  This is not good for perfomance   In the junit  inside Corematchers  there s a matcher for this    hasItems  List lt Integer gt  yourList   Arrays asList 1 2 3 4      assertThat yourList  CoreMatchers hasItems 1 2 3 4 5      This is the better way that I know of to check elements in a list

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I know there are already many options to solve this issue  but I would rather do the following to assert two lists in any oder   assertTrue result containsAll expected   amp  amp  expected containsAll result

User · Answer

This is a legacy answer  suitable for JUnit 4 3 and below  The modern version of JUnit includes a built-in readable failure messages in the assertThat method  Prefer other answers on this question  if possible   List lt E gt  a   resultFromTest    List lt E gt  expected   Arrays asList new E    new E          assertTrue  Expected  a  and  expected  to be equal                  n   a             a                n   expected      expected               expected equals a      For the record  as  Paul mentioned in his comment to this answer  two Lists are equal      if and only if the specified object is also a list  both lists have the same size  and all corresponding pairs of elements in the two lists are equal   Two elements e1 and e2 are equal if  e1  null   e2  null   e1 equals e2     In other words  two lists are defined to be equal if they contain the same elements in the same order  This definition ensures that the equals method works properly across different implementations of the List interface    See the JavaDocs of the List interface

[java] Assert equals between 2 Lists in Junit

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