Hamcrest

Hamcrest比起JUnit的assert系列方法来，有更好的可读性，它按照参数从左到右的符合自然的顺序来展示，如actual is(notNullValue())，是对测试断言的改进。同时不会被哪个参数是actual，哪个是expect而混淆。除此之外，Hamcrest提供了更丰富的比较方法，不仅包括基本类型，也包括对象判断、集合/数组判断等一系列方法，同时还有allOf/anyOf这样的组合判断，甚至有判断xml中是否存在相应xpath的判断。

所有的Hamcrest支持的assert全部在org.hamcrest.Matchers类下的静态方法。下面是几个使用例子:

public class CoreShowcase {
    @Test
    public void test(){
        assertThat(true,is(true));
        assertThat(false,is(false));

        assertThat("2",is(equalTo("2")));
        assertThat(2,is(equalTo(2)));
        assertThat("aBcD",is(equalToIgnoringCase("abcd")));
        assertThat("",isEmptyOrNullString());

        assertThat(null,is(nullValue()));
        assertThat(2,is(notNullValue()));
        assertThat(2,greaterThan(1));
        assertThat(2.01,closeTo(2,0.01));

        assertThat("xyz",is(anything()));
    }
}

　　

public class ObjectShowcase {
    @Test
    public void test(){
        Person my=new Person("341024","ZhangKe",32);

        assertThat(my,instanceOf(Person.class));
        assertThat(my,not(sameInstance(new Person("341024"))));
        assertThat(my,hasToString(equalTo("341024")));
        assertThat(my,hasProperty("name"));
    }

    class Person{
        private String idCard;
        private String name;
        private int age;

        public Person(String idCard) {
            this.idCard = idCard;
        }

        public Person(String idCard, String name, int age) {
            this.idCard = idCard;
            this.name = name;
            this.age = age;
        }

        public String getIdCard() {
            return idCard;
        }

        public String getName() {
            return name;
        }

        public int getAge() {
            return age;
        }

        @Override
        public String toString() {
            return idCard;
        }

        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;

            Person person = (Person) o;

            if (!idCard.equals(person.idCard)) return false;

            return true;
        }

        @Override
        public int hashCode() {
            return idCard.hashCode();
        }
    }
}

　　

public class CombineShowcase {
    @Test
    public void test(){
        //in both/either must have the same type
        assertThat("result", both(containsString("r")).and(containsString("u")));
        assertThat("result",either(startsWith("x")).or(containsString("r")));

        assertThat("result",allOf(notNullValue(),containsString("s")));
        assertThat("result",anyOf(notNullValue(),isEmptyString()));
    }
}