JAVA

in a junit test how test if empty list is returned

You can simply use

assertFalse(result.isEmpty());
or
assertThat(items, IsCollectionWithSize.hasSize(greaterThan(1)))
Regarding your problem, it's simply caused by the fact that you forgot to statically import the is() method from Hamcrest;

import static org.hamcrest.CoreMatchers.is;