Assertj-core: `isEqualToComparingFieldByFieldRecursively` throws NullPointerException while comparing null values

Created on 5 Jan 2018 · 7Comments · Source: assertj/assertj-core

Summary

If a nested field is null while comparing equality for two objects with isEqualToComparingFieldByFieldRecursively a NullPointerException is thrown.

Stacktrace

Exception in thread "main" java.lang.NullPointerException
    at org.assertj.core.error.ShouldBeEqualByComparingFieldByFieldRecursively.describeDifference(ShouldBeEqualByComparingFieldByFieldRecursively.java:67)
    at org.assertj.core.error.ShouldBeEqualByComparingFieldByFieldRecursively.shouldBeEqualByComparingFieldByFieldRecursive(ShouldBeEqualByComparingFieldByFieldRecursively.java:32)
    at org.assertj.core.internal.Objects.assertIsEqualToComparingFieldByFieldRecursively(Objects.java:728)
    at org.assertj.core.api.AbstractObjectAssert.isEqualToComparingFieldByFieldRecursively(AbstractObjectAssert.java:653)
...

Example

class Main {

    static class Value {
        private final String v;

        public Value(String v) {
            this.v = v;
        }
    }

    public static void main(String[] args) {
        Value actual = new Value(null); //swapping actual and expected leads to the same error
        Value expected = new Value("something");
        Assertions.assertThat(expected).isEqualToComparingFieldByFieldRecursively(actual);
    }

}