junit之断言

断言 	描述
void assertEquals([String message], expected value, actual value) 	断言两个值相等。值可能是类型有 int, short, long, byte, char or java.lang.Object. 第一个参数是一个可选的字符串消息
void assertTrue([String message], boolean condition) 	断言一个条件为真
void assertFalse([String message],boolean condition) 	断言一个条件为假
void assertNotNull([String message], java.lang.Object object) 	断言一个对象不为空(null)
void assertNull([String message], java.lang.Object object) 	断言一个对象为空(null)
void assertSame([String message], java.lang.Object expected, java.lang.Object actual) 	断言，两个对象引用相同的对象
void assertNotSame([String message], java.lang.Object unexpected, java.lang.Object actual) 	断言，两个对象不是引用同一个对象
void assertArrayEquals([String message], expectedArray, resultArray) 	断言预期数组和结果数组相等。数组的类型可能是 int, long, short, char, byte or java.lang.Object.

下面是来自junit官方的一个例子：
import static org.hamcrest.CoreMatchers.allOf;
import static org.hamcrest.CoreMatchers.anyOf;
import static org.hamcrest.CoreMatchers.both;
import static org.hamcrest.CoreMatchers.containsString;
import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.CoreMatchers.everyItem;
import static org.hamcrest.CoreMatchers.hasItems;
import static org.hamcrest.CoreMatchers.not;
import static org.hamcrest.CoreMatchers.sameInstance;
import static org.hamcrest.CoreMatchers.startsWith;
import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertNotSame;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertSame;
import static org.junit.Assert.assertThat;
import static org.junit.Assert.assertTrue;

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();
        assertArrayEquals("failure - byte arrays not same", expected, actual);
    }

    @Test
    public void testAssertEquals() {
        assertEquals("failure - strings are not equal", "text", "text");
    }

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

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

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

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

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

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

    @Test
    public void testAssertThatHasItems() {
        assertThat(Arrays.asList("one", "two", "three"), hasItems("one", "three"));
    }

    @Test
    public void testAssertThatEveryItemContainsString() {
        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())));
    }

    @Test
    public void testAssertTrue() {
        assertTrue("failure - should be true", true);
    }
}