Assert equals 2 lists

Question

Trying to assert 2 lists but it fails:

I'm trying to compare two List objects.

Here's my test class.

public class RestServiceTest {

    HttpClient http = new HttpClient();
    private Gson gson = new Gson();

    @Test
    public void getAllEmployeesTest() throws IOException {
        HttpResponse response = http.get("http://localhost:8087/employee");
        List<Employee> expectedList = new ArrayList<>();
        expectedList.add(new Employee(2, "Yashwant", "Chavan", 30, false));
        Type listType = new TypeToken<ArrayList<Employee>>() {}.getType();

        List<Employee> actualList = gson.fromJson(EntityUtils.toString(response.getEntity()), listType);
        System.out.println(actualList);
        System.out.println(expectedList);
        Assert.assertEquals(actualList,expectedList);
    }
}

Have you overridden `equals` (and `hashCode`) in `Employee`? — Andy Turner, May 29 '18 at 14:36
Note that the arguments are the other way around. It's `assertEquals(expected, actual)`. — Zabuzard, May 29 '18 at 15:23

KoenC · Accepted Answer · 2018-05-30T08:46:27.113

Seeing your code, you add a new Employee in your expectedList giving that object a unique reference. The actual list will have another instance of Employee with another unique reference making these two different objects.

Although the two objects have the same fields, the assertEquals for list will use the equals method within Employee to check if the objects are the same. If you haven't implemented the equals method yourself inside Employee it will check on those unique references I mentioned before.

A solution would be to override the equals method in Employee like this:

@Override
public boolean equals(Object obj) {
   if(!obj instanceof Employee) {
      return false;
   }
   Employee e = (Employee) obj;
   // Add more fields to compare if necessary
   return this.getEmployeeId().equals(e.getEmployeeId()) && this.getAge().equals(e.getAge()); 
 }

which should give you the results you're hoping for. Possible similar issue and probably better explanation.

As mentioned by @Zabuza you also need to override hashCode as well in case you use something like a HashMap in combination with Employee. Further explanation about `hashCode can be found here.

Don't forget to mention that when overriding `equals` one **must** always override `hashCode` too. Else *terrible things* will happen. — Zabuzard, May 29 '18 at 15:25
@Zabuza valid point, I added a reference to an other question addressing `hashCode` — KoenC, May 30 '18 at 08:47

score 0 · Answer 2 · answered May 29 '18 at 14:39

See the Collection documentation: you should implement/override equals method. Otherwise when comparing two collections (e.g. Lists of Employees) each item will be compared on its object id. (Also, remember to implement Employee.hashCode() method too.)

score 0 · Answer 3 · answered May 29 '18 at 14:50

0

In case of comparing lists I highly recommend to move to assertJ: http://joel-costigliola.github.io/assertj/

Using that that assert would be:

Assertions.assertThat(actualList).containsAll(expectedList);

answered May 29 '18 at 14:50

padilo

996
9
18

Changing the method for checking if the two lists are equal does not really apply here. `Assert.assertEquals` does the trick. – KoenC May 30 '18 at 08:50

Assert equals 2 lists

3 Answers3