CollectionAssert in jUnit?

Question

Is there a jUnit parallel to NUnit's CollectionAssert?

Answer 1

Using JUnit 4.4 you can use assertThat() together with the Hamcrest code (don't worry, it's shipped with JUnit, no need for an extra .jar) to produce complex self-describing asserts including ones that operate on collections:

import static org.junit.Assert.assertThat;
import static org.junit.matchers.JUnitMatchers.*;
import static org.hamcrest.CoreMatchers.*;

List<String> l = Arrays.asList("foo", "bar");
assertThat(l, hasItems("foo", "bar"));
assertThat(l, not(hasItem((String) null)));
assertThat(l, not(hasItems("bar", "quux")));
// check if two objects are equal with assertThat()

// the following three lines of code check the same thing.
// the first one is the "traditional" approach,
// the second one is the succinct version and the third one the verbose one 
assertEquals(l, Arrays.asList("foo", "bar")));
assertThat(l, is(Arrays.asList("foo", "bar")));
assertThat(l, is(equalTo(Arrays.asList("foo", "bar"))));

Using this approach you will automagically get a good description of the assert when it fails.