Hamcrest is a neat little library that lets you write more fluent and readable tests. For example, rather than writing:

    assertEquals("red", color);

you would write:

    assertThat(color,is("red"));

A version of Hamcrest is actually bundled with JUnit. However it is somewhat dated, and the more recent versions of Hamcrest come with a lot more features, particularly with regards to working with collections. You can use the latest version of Hamcrest by using the junit-dep dependency instead of junit, and configuring your dependencies as shown here:

 <dependency>
	    <groupId>junit</groupId>
	    <artifactId>junit-dep</artifactId>
	    <version>4.10</version>
	    <scope>test</scope>
	    <exclusions>
	        <exclusion>
	            <groupId>org.hamcrest</groupId>
	            <artifactId>hamcrest-core</artifactId>
	        </exclusion>
	    </exclusions>
	</dependency>
	<dependency>
	    <groupId>org.hamcrest</groupId>
	    <artifactId>hamcrest-library</artifactId>
	    <version>1.3.RC2</version>
	</dependency>

You can check the size of a collection directly:

    List colors = Arrays.asList("red","green","blue");
    assertThat(colors, hasSize(3));

 List colors = Arrays.asList("red","green","blue");
    assertThat(colors, contains("red", "green", "blue"));

This last example checks both the contents and the order of the collection. If you are only interested in the contents, you can use containsInAnyOrder:

   List colors = Arrays.asList("red","green","blue");
    assertThat(colors, containsInAnyOrder("green", "red", "blue"));

You can also check that a condition is true for every item in a list:

    List ages = Arrays.asList(21, 25,30);
    assertThat(ages, everyItem(greaterThan(18)));

This version is a release candidate, so there might be a few rough edges before the final version. And since the artifact names have changed, you need to be careful to exclude any references to hamcrest-all used by other libraries (lambdaj, for example, uses Hamcrest).

From http://weblogs.java.net/blog/johnsmart/archive/2011/12/12/some-useful-new-hamcrest-matchers-collections