Junit Assertion Error for ArrayList and Arrays.asList()

Question

I have method which returns ArrayList of object as below -

public <Range> getAllRanges(List<Range> ranges){
  //Some business logic
  ....
  List<Range> resultRanges = new ArrayList<>();
  .....
  return resultRanges;
}

I am writing Junit for this as -

@Test
public void someInputTest() {
    final List<Range> ranges = Arrays.asList(new Range(1, 3), new Range(2, 4));
    final List<Range> actual = myCalss.getAllRanges(ranges);
    final List<Range> expected = Arrays.asList(new Range(1, 4));
    assertEquals(expected, actual);
}

but I am getting Assertion Error like -

java.lang.AssertionError: expected: java.util.Arrays$ArrayList<[(1, 4)]> but was: java.util.ArrayList<[(1, 4)]>
....

After that I tried below code in test -

@Test
public void someInputTest() {
    final List<Range> ranges = Arrays.asList(new Range(1, 3), new Range(2, 4));
    final List<Range> actual = myCalss.getAllRanges(ranges);
    final List<Range> expected = new ArrayList<>();
    expected.add(new Range(1, 4));
    assertEquals(expected, actual);
}

but after that I am getting -

java.lang.AssertionError: expected: java.util.ArrayList<[(1, 4)]> but was: java.util.ArrayList<[(1, 4)]>
...

Now expected and actual are bot same but still assertion error. What I am doing wrong here.

This is basic Java. You are comparing two different Objects. Of course they are not equal... Add dependency for Hamcrest library, and add assertion like: assertThat(list1, containsInAnyOrder(list2.toArray())); — Dezso Gabos
– Dezso Gabos, Commented Mar 3, 2019 at 20:34
Two lists are equal if their corresponding elements are equal (and have the same length), so assertEquals is perfectly fine for testing two lists for equality. Make sure you have (correctly) implemented the equals method for Range class. E.g make sure this assertion passes: assertEquals(new Range(1, 4), new Range(1, 4)) — binoternary
– binoternary, Commented Mar 3, 2019 at 21:17

Vic Seedoubleyew · Accepted Answer · 2019-06-25 14:17:23Z

5

Weirdly enough, Arrays.asList hasn't overridden equals, and thus even if it contains the same elements as another list of type ArrayList, they will not be compared as equal.

One solution is to wrap it into an ArrayList:

assertEquals(new ArrayList<>(Arrays.asList(...)), myArrayList);

answered Jun 25, 2019 at 14:17

Vic Seedoubleyew

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Shaiq_Huseynzade · Accepted Answer · 2020-03-29 18:13:24Z

2

I had the same problem.You should add in your class , which used in list, equals and hashcode . After that it will work.

answered Mar 29, 2020 at 18:13

Shaiq_Huseynzade

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pushpendra singh Parmar · Accepted Answer · 2022-05-06 08:34:09Z

0

Adding Equals and Hashcode methods in the object which is being used in Arraylist will surely help in the case of assertEquals for arraylists of user defined objects.

answered May 6, 2022 at 8:34

pushpendra singh Parmar

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Kai-Sheng Yang · Accepted Answer · 2022-05-07 16:31:56Z

0

A quick and easy way: just simply add @EqualsAndHashCode on your Range class. @EqualsAndHashCode is provided by Project Lombok and generates hashCode and equals implementations from the fields of your object.

@EqualsAndHashCode
public class Range {
   private int x;
   // ...
}

And the following assertion works well in JUnit 4.13.1

Assert.assertEquals(expectedArrayList, actualArrayList);

https://projectlombok.org/features/EqualsAndHashCode

answered May 7, 2022 at 16:31

Kai-Sheng Yang

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