How to use JUnit and Hamcrest together?

Question

I can't understand how JUnit 4.8 should work with Hamcrest matchers. There are some matchers defined inside junit-4.8.jar in org.hamcrest.CoreMatchers. At the same time there are some other matchers in hamcrest-all-1.1.jar in org.hamcrest.Matchers. So, where to go? Shall I explicitly include hamcrest JAR into the project and ignore matchers provided by JUnit?

In particular, I'm interested in empty() matcher and can't find it in any of these jars. I need something else? :)

And a philosophical question: why JUnit included org.hamcrest package into its own distribution instead of encouraging us to use original hamcrest library?

Answer 1

junit provides new check assert methods named assertThat() which uses Matchers and should provide a more readable testcode and better failure messages.

To use this there are some core matchers included in junit. You can start with these for basic tests.

If you want to use more matchers you can write them by yourself or use the hamcrest lib.

The following example demonstrates how to use the empty matcher on an ArrayList:

package com.test;

import static org.hamcrest.Matchers.empty;
import static org.hamcrest.Matchers.is;
import static org.junit.Assert.assertThat;

import java.util.ArrayList;
import java.util.List;

import org.junit.Test;

public class EmptyTest {
    @Test
    public void testIsEmpty() {
        List myList = new ArrayList();
        assertThat(myList, is(empty()));

    }
}

(I included the hamcrest-all.jar in my buildpath)