AssertJ网站:  http://joel-costigliola.github.io/assertj/

github上examples 地址  https://github.com/joel-costigliola/assertj-examples

附件中assertj-examples-octo-assertj-core-1.5.0是官方examples

整理一些常用的例子如下

对字符串断言

@Test
	public void testString() {
		String str = null;
		// 断言null或为空字符串
		assertThat(str).isNullOrEmpty();
		// 断言空字符串
		assertThat("").isEmpty();
		// 断言字符串相等 断言忽略大小写判断字符串相等
		assertThat("Frodo").isEqualTo("Frodo").isEqualToIgnoringCase("frodo");
		// 断言开始字符串 结束字符穿 字符串长度
		assertThat("Frodo").startsWith("Fro").endsWith("do").hasSize(5);
		// 断言包含字符串 不包含字符串
		assertThat("Frodo").contains("rod").doesNotContain("fro");
		// 断言字符串只出现过一次
		assertThat("Frodo").containsOnlyOnce("do");
		// 判断正则匹配
		assertThat("Frodo").matches("..o.o").doesNotMatch(".*d");
	}

对数字断言

@Test
	public void testNumber() {
		Integer num = null;
		// 断言空
		assertThat(num).isNull();
		// 断言相等
		assertThat(42).isEqualTo(42);
		// 断言大于 大于等于
		assertThat(42).isGreaterThan(38).isGreaterThanOrEqualTo(38);
		// 断言小于 小于等于
		assertThat(42).isLessThan(58).isLessThanOrEqualTo(58);
		// 断言0
		assertThat(0).isZero();
		// 断言正数 非负数
		assertThat(1).isPositive().isNotNegative();
		// 断言负数 非正数
		assertThat(-1).isNegative().isNotPositive();
	}

 对日期断言

@Test
    public void testDate() {
	// 断言与指定日期相同 不相同 在指定日期之后 在指定日期之钱
	assertThat(Dates.parse("2014-02-01")).isEqualTo("2014-02-01").isNotEqualTo("2014-01-01")
		.isAfter("2014-01-01").isBefore(parse("2014-03-01"));
	// 断言 2014 在指定年份之前 在指定年份之后
	assertThat(DateTime.now().toDate()).isBeforeYear(2020).isAfterYear(2013);
	// 断言时间再指定范围内 不在指定范围内
	assertThat(parse("2014-02-01")).isBetween("2014-01-01", "2014-03-01").isNotBetween(
		parse("2014-02-02"), parse("2014-02-28"));
<span class="hljs-comment">// 断言两时间相差100毫秒</span>
<span class="hljs-built_in">Date</span> d1 = <span class="hljs-keyword">new</span> <span class="hljs-built_in">Date</span>();
<span class="hljs-built_in">Date</span> d2 = <span class="hljs-keyword">new</span> <span class="hljs-built_in">Date</span>(d1.getTime() + <span class="hljs-number">100</span>);
assertThat(d1).isCloseTo(d2, <span class="hljs-number">100</span>);

<span class="hljs-comment">// sets dates differing more and more from date1</span>
<span class="hljs-built_in">Date</span> date1 = Dates.parseDatetimeWithMs(<span class="hljs-string">"2003-01-01T01:00:00.000"</span>);
<span class="hljs-built_in">Date</span> date2 = parseDatetimeWithMs(<span class="hljs-string">"2003-01-01T01:00:00.555"</span>);
<span class="hljs-built_in">Date</span> date3 = parseDatetimeWithMs(<span class="hljs-string">"2003-01-01T01:00:55.555"</span>);
<span class="hljs-built_in">Date</span> date4 = parseDatetimeWithMs(<span class="hljs-string">"2003-01-01T01:55:55.555"</span>);
<span class="hljs-built_in">Date</span> date5 = parseDatetimeWithMs(<span class="hljs-string">"2003-01-01T05:55:55.555"</span>);

<span class="hljs-comment">// 断言 日期忽略毫秒,与给定的日期相等</span>
assertThat(date1).isEqualToIgnoringMillis(date2);
<span class="hljs-comment">// 断言 日期与给定的日期具有相同的年月日时分秒</span>
assertThat(date1).isInSameSecondAs(date2);
<span class="hljs-comment">// 断言 日期忽略秒,与给定的日期时间相等</span>
assertThat(date1).isEqualToIgnoringSeconds(date3);
<span class="hljs-comment">// 断言 日期与给定的日期具有相同的年月日时分</span>
assertThat(date1).isInSameMinuteAs(date3);
<span class="hljs-comment">// 断言 日期忽略分,与给定的日期时间相等</span>
assertThat(date1).isEqualToIgnoringMinutes(date4);
<span class="hljs-comment">// 断言 日期与给定的日期具有相同的年月日时</span>
assertThat(date1).isInSameHourAs(date4);
<span class="hljs-comment">// 断言 日期忽略小时,与给定的日期时间相等</span>
assertThat(date1).isEqualToIgnoringHours(date5);
<span class="hljs-comment">// 断言 日期与给定的日期具有相同的年月日</span>
assertThat(date1).isInSameDayAs(date5);
}</pre>

对List断言

@Test
	public void testList() {
		// 断言 列表是空的
		assertThat(newArrayList()).isEmpty();
		// 断言 列表的开始 结束元素
		assertThat(newArrayList(1, 2, 3)).startsWith(1).endsWith(3);
		// 断言 列表包含元素 并且是排序的
		assertThat(newArrayList(1, 2, 3)).contains(1, atIndex(0)).contains(2, atIndex(1)).contains(3)
				.isSorted();
		// 断言 被包含与给定列表
		assertThat(newArrayList(3, 1, 2)).isSubsetOf(newArrayList(1, 2, 3, 4));
		// 断言 存在唯一元素
		assertThat(Lists.newArrayList("a", "b", "c")).containsOnlyOnce("a");
	}

对Map断言

@Test
    public void testMap() {
	Map<String, Object> foo = Maps.newHashMap();
	foo.put("A", 1);
	foo.put("B", 2);
	foo.put("C", 3);
<span class="hljs-comment">// 断言 map 不为空 size</span>
assertThat(foo).isNotEmpty().hasSize(<span class="hljs-number">3</span>);
<span class="hljs-comment">// 断言 map 包含元素</span>
assertThat(foo).contains(entry(<span class="hljs-string">"A"</span>, <span class="hljs-number">1</span>), entry(<span class="hljs-string">"B"</span>, <span class="hljs-number">2</span>));
<span class="hljs-comment">// 断言 map 包含key</span>
assertThat(foo).containsKeys(<span class="hljs-string">"A"</span>, <span class="hljs-string">"B"</span>, <span class="hljs-string">"C"</span>);
<span class="hljs-comment">// 断言 map 包含value</span>
assertThat(foo).containsValue(<span class="hljs-number">3</span>);
}</pre>

对Class断言

@Test
	public void testClass() {
		// 断言 是注解
		assertThat(Magical.class).isAnnotation();
		// 断言 不是注解
		assertThat(Ring.class).isNotAnnotation();
		// 断言 存在注解
		assertThat(Ring.class).hasAnnotation(Magical.class);
		// 断言 不是借口
		assertThat(Ring.class).isNotInterface();
		// 断言 是否为指定Class实例
		assertThat("string").isInstanceOf(String.class);
		// 断言 类是给定类的父类
		assertThat(Person.class).isAssignableFrom(Employee.class);
	}
<span class="hljs-meta">@Magical</span>
public enum <span class="hljs-type">Ring</span> {
	oneRing, vilya, nenya, narya, dwarfRing, manRing;
}
<span class="hljs-meta">@Target</span>(<span class="hljs-type">ElementType</span>.<span class="hljs-type">TYPE</span>)
<span class="hljs-meta">@Retention</span>(<span class="hljs-type">RetentionPolicy</span>.<span class="hljs-type">RUNTIME</span>)
public <span class="hljs-meta">@interface</span> <span class="hljs-type">Magical</span> {}
public <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Person</span> </span>{}
public <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Employee</span> <span class="hljs-keyword">extends</span> <span class="hljs-title">Person</span> </span>{}</pre>

使用fail方法

@Test
    public void testFail() {
        fail("在不检查任何条件的情况下使断言失败。显示一则消息");
    }
除此之外,还提供包括Exception、Iterable、JodaTime、Guava等等很多的断言支持。