@Test
void testEquals() {

    final ToLongNullable<String> copy = instance;
    assertTrue(instance.equals(copy));
    assertFalse(instance.equals(null));
    final ToLongNullable<String> another = new ToLongNullableImpl<>(
        instance.inner(),
        instance.isNullPredicate()
    );
    final ToLongNullable<String> originalSame = new ToLongNullableImpl<>(
        instance.inner(),
        Objects::isNull
    );
    final ToLongNullable<String> isNullSame = new ToLongNullableImpl<>(
        String::length,
        instance.isNullPredicate()
    );
    assertTrue(instance.equals(another));
    assertFalse(instance.equals(originalSame));
    assertFalse(instance.equals(isNullSame));
}