Hamcrest matchers in junit

Junit 4.8+ onwards provides one assertion method called as assertthat. assertThat method takes hamcrest matchers as arguments. Below class contains all static methods used along with assertThat

 
org.hamcrest.CoreMatchers

Important methods in CoreMatchers class are given below.

• is
• not
• nullValue
• notNullValue
• sameInstance
• containsString
• allOf
• anyOf
• equalTo
• hasItems

Below example shows how to use hamcrest matchers in JUnit tests.

 
package hamcrest;
import org.junit.Assert;
import org.junit.Ignore;
import org.junit.Test;

import java.util.Arrays;
import java.util.List;
import static org.junit.Assert.assertThat;

import static org.hamcrest.CoreMatchers.*;

    public class TestHamcrest {

        @Test
        public void hi(){

            TestHamcrest m1 = new TestHamcrest();
            TestHamcrest m2 = m1;
            TestHamcrest m3 = null;

            //is matcher
            Assert.assertThat(111,is(100+11));
            Assert.assertThat(111,is(not(100+12)));
            assertThat(new String[]{"junit", "hamcrest"}, is(new String[]{"junit", "hamcrest"}));

            //verification of null values
            assertThat(m3, nullValue());
            assertThat(m2, notNullValue());

            //checking if both variables point to same object
            assertThat(m1, sameInstance(m2));

            //String verifications
            assertThat("hamcrest", containsString("ham"));

            //assertions with list
            List<Integer> list = Arrays.asList(5, 2, 4);
            assertThat(list, hasItems(2, 5));

            //all of - used to make multiple assertions at a time
            assertThat(4.12, is(allOf(notNullValue(), instanceOf(Double.class), equalTo(4.12))));

            //any of - used to make multiple assertions at a time
            assertThat(4.12, is(anyOf(notNullValue(), instanceOf(String.class), equalTo(4.11))));

            //equalTo
            assertThat("Junit", is(equalTo("Junit")));

            //instanceOf
            assertThat("Junit", is(instanceOf(String.class)));

            //any of - used to make multiple assertions at a time
            assertThat(4.12, is(anyOf(notNullValue(), instanceOf(String.class), equalTo(4.11))));

        }

}