Rewriting "assertTrue" into "assertThat" in JUnit?

Question

List<String> list1 = getListOne();
List<String> list2 = getListTwo();

Given the code above, I want to use a JUnit assertThat() statement to assert that either list1 is empty or that list1 contains all the elements of list2. The assertTrue equivalent of this is:

assertTrue(list1.isEmpty() || list1.containsAll(list2)).

How to formulate this into an assertThat statement?

Thanks.

Answer 1

You can do this in the following way:

// Imports
import static org.hamcrest.CoreMatchers.either;
import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.collection.IsEmptyIterable.emptyIterableOf;
import static org.hamcrest.core.IsCollectionContaining.hasItems;
import static org.junit.Assert.assertThat;
import static org.hamcrest.CoreMatchers.is;

// First solution
assertThat(list1,
    either(emptyIterableOf(String.class))
    .or(hasItems(list2.toArray(new String[list2.size()]))));

// Second solution, this will work ONLY IF both lists have items in the same order.
assertThat(list1,
    either(emptyIterableOf(String.class))
        .or(is((Iterable<String>) list2)));