How to test anonymous inner classes

[Tom Wieczorek]

Consider a class like this:

public abstract class Foo<T> {
    public static <T> Foo<T> of(T value) {
        Objects.requireNonNull(value);
        return new Foo<T>() {
            @Override
            public String toString() {
                return String.format("Foo.of(%s)", value);
            }

            @Override
            public boolean equals(Object obj) {
                    return obj != null && getClass() == obj.getClass() && value.equals(((Foo<?>) obj).get());
            }

            @Override
            public int hashCode() {
                return Objects.hash(getClass(), value);
            }

            @Override
            public T get() {
                return value;
            }
        };
    }

    public abstract T get();
}

I failed to write a working EqualsVerifier test for the instances returned by Foo::of.

The culprit is that the actual value that's held by Foo instances created by of() is a synthetic field, and therefore is skipped by EqualsVerifier. I cannot provide examples for a relaxed equality check, too, since we need to have two equal instances which have at least one non-equal member (which also won't work with the above class structure).

Any ideas?

Thanks,

Tom.