Why does this not compile, oh, what to do?
import static org.junit.Assert.assertThat;
import static org.junit.matchers.JUnitMatchers.hasItems;
ArrayList<
You can get this error if you try to replace jUnit's hamcrest with a newer version. For example, using junit-dep together with hamcrest 1.3 requires that use assertThat from hamcrest instead of jUnit.
So the solution is to use
import static org.hamcrest.MatcherAssert.assertThat;
instead of
import static org.junit.Assert.assertThat;