Assertions

JUnit provides overloaded assertion methods for all primitive types and Objects and arrays (of primitives or Objects). The parameter order is expected value followed by actual value. Optionally the first parameter can be a String message that is output on failure. There is a slightly different assertion, assertThat that has parameters of the optional failure message, the actual value, and a Matcher object. Note that expected and actual are reversed compared to the other assert methods.

Examples

A representative of each assert method is shown.

import static org.hamcrest.CoreMatchers.allOf;
import static org.hamcrest.CoreMatchers.anyOf;
import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.CoreMatchers.not;
import static org.hamcrest.CoreMatchers.sameInstance;
import static org.hamcrest.CoreMatchers.startsWith;
import static org.junit.Assert.assertThat;
import static org.junit.matchers.JUnitMatchers.both;
import static org.junit.matchers.JUnitMatchers.containsString;
import static org.junit.matchers.JUnitMatchers.everyItem;
import static org.junit.matchers.JUnitMatchers.hasItems;

import java.util.Arrays;

import org.hamcrest.core.CombinableMatcher;
import org.junit.Test;

public class AssertTests {
	@Test
	public void testAssertArrayEquals() {
		byte[] expected = "trial".getBytes();
		byte[] actual = "trial".getBytes();
		org.junit.Assert.assertArrayEquals("failure - byte arrays not same", expected, actual);
	}

	@Test
	public void testAssertEquals() {
		org.junit.Assert.assertEquals("failure - strings not same", 5l, 5l);
	}

	@Test
	public void testAssertFalse() {
		org.junit.Assert.assertFalse("failure - should be false", false);
	}

	@Test
	public void testAssertNotNull() {
		org.junit.Assert.assertNotNull("should not be null", new Object());
	}

	@Test
	public void testAssertNotSame() {
		org.junit.Assert.assertNotSame("should not be same Object", new Object(), new Object());
	}

	@Test
	public void testAssertNull() {
		org.junit.Assert.assertNull("should be null", null);
	}

	@Test
	public void testAssertSame() {
		Integer aNumber = Integer.valueOf(768);
		org.junit.Assert.assertSame("should be same", aNumber, aNumber);
	}

	// JUnit Matchers assertThat
	@Test
	public void testAssertThatBothContainsString() {
		org.junit.Assert.assertThat("albumen", both(containsString("a")).and(containsString("b")));
	}

	@Test
	public void testAssertThathasItemsContainsString() {
		org.junit.Assert.assertThat(Arrays.asList("one", "two", "three"), hasItems("one", "three"));
	}

	@Test
	public void testAssertThatEveryItemContainsString() {
		org.junit.Assert.assertThat(Arrays.asList(new String[] { "fun", "ban", "net" }), everyItem(containsString("n")));
	}

	// Core Hamcrest Matchers with assertThat
	@Test
	public void testAssertThatHamcrestCoreMatchers() {
		assertThat("good", allOf(equalTo("good"), startsWith("good")));
		assertThat("good", not(allOf(equalTo("bad"), equalTo("good"))));
		assertThat("good", anyOf(equalTo("bad"), equalTo("good")));
		assertThat(7, not(CombinableMatcher.<Integer> either(equalTo(3)).or(equalTo(4))));
		assertThat(new Object(), not(sameInstance(new Object())));
	}