AssertJ Core, is it possible to get error message with actual field/property difference when checking iterables/arrays content?

Question

In Assertj Core you can compare ojects field by field recursively.

In this test address.countryCode differ in the two objects:

@Test
public void shouldBeEqual() {
    Person person1 = createPerson();
    Person person2 = createPerson2();
    assertThat(person1)
            .usingRecursiveComparison()
            .isEqualTo(person2);
}

I get error gessage:

java.lang.AssertionError: 
Expecting actual:
  Person@4b44655e
to be equal to: 
  Person@290d210d
when recursively comparing field by field, but found the following difference:

field/property 'address.countryCode' differ:
- actual value  : "US"
- expected value: "CA"

The recursive comparison was performed with this configuration:
- no overridden equals methods were used in the comparison (except for java types)
- these types were compared with the following comparators:
  - java.lang.Double -> DoubleComparator[precision=1.0E-15]
  - java.lang.Float -> FloatComparator[precision=1.0E-6]
  - java.nio.file.Path -> lexicographic comparator (Path natural order)
- actual and expected objects and their fields were compared field by field recursively even if they were not of the same type, this allows for example to compare a Person to a PersonDto (call strictTypeChecking(true) to change that behavior).

When you get the actual field difference in the error message like above it is very helpful, but if I have a list and want to verify the content of the list:

@Test
public void shouldBeEqual2() {
    List<Person> personList = List.of(createPerson(), createPerson2());

    assertThat(personList)
            .hasSize(2)
            .usingRecursiveFieldByFieldElementComparator()
            .containsExactlyInAnyOrder(createPerson(), createPerson());
}

I get error message:

java.lang.AssertionError: 
Expecting actual:
  [Person@4fe767f3, Person@18ce0030]
to contain exactly in any order:
  [Person@2805c96b, Person@4445629]
elements not found:
  [Person@4445629]
and elements not expected:
  [Person@18ce0030]
when comparing values using recursive field/property by field/property comparator on all fields/properties using the following configuration:
- no overridden equals methods were used in the comparison (except for java types)
- these types were compared with the following comparators:
  - java.lang.Double -> DoubleComparator[precision=1.0E-15]
  - java.lang.Float -> FloatComparator[precision=1.0E-6]
  - java.nio.file.Path -> lexicographic comparator (Path natural order)
- actual and expected objects and their fields were compared field by field recursively even if they were not of the same type, this allows for example to compare a Person to a PersonDto (call strictTypeChecking(true) to change that behavior).

Is it not possible to get the actual field difference here like in the first example?

score 1 · Accepted Answer · answered Mar 21 '22 at 09:48

It is not possible at the moment because the error message built for containsExactlyInAnyOrder is not aware of the root cause of the assertion failure, in our case it does not know the comparison differences, it only knows that the assertion failed and build a generic error message.

We already have thought of supporting this use case but it is not straightforward to implement with the current way errors are designed.

AssertJ Core, is it possible to get error message with actual field/property difference when checking iterables/arrays content?

1 Answers1