Recursive comparison

The recursive comparison feature of AssertJ allows you to compare complex objects by recursively comparing their fields. This is particularly useful when you want to verify that two objects are equivalent in terms of their state, without having to write custom equals methods or manually compare each field.

RecursiveComparisonTest.java

import org.junit.jupiter.api.Test;

import static org.assertj.core.api.Assertions.assertThat;

class RecursiveComparisonTest {

    @Test
    void compareFieldsIgnoringYear() {
        Book hardcover = new Book("Effective Java", "Joshua Bloch", 2001);
        Book paperback = new Book("Effective Java", "Joshua Bloch", 2018);

        // Compare all fields except 'year'
        assertThat(hardcover)
                .usingRecursiveComparison()
                .ignoringFields("year")
                .isEqualTo(paperback);
    }
}

tip

Note how ignoringFields("year") is used to exclude the year field from the recursive comparison. This is especially useful when certain fields are expected to differ, such as timestamps or IDs.