JUnit的好搭档-Hamcrest

一、Hamcrest简介

　　Hamcrest是一个用于编写匹配器（matcher）对象的框架，允许以声明方式定义“匹配（match）”规则。它可以与JUnit框架配合使用，使断言可读更高，更加灵活（例如判断数组、集合、map中的内容等）。

Hamcrest支持多种语言，本文只使用JAVA语言。Hamcrest官网：http://hamcrest.org/

二、Java Hamcrest 常用匹配器

    @Test
    public void testAssertThatWithHamcrest() {

        /**
         * 核心：
         */
        //anything：总是匹配,如果你不关心测试下的对象是什么是有用的
        assertThat("随便是个啥", anything("总是匹配就完事了"));
        //describedAs：添加一个定制的失败表述装饰器
        assertThat("zs", describedAs("自定义故障描述",equalTo("zs")));
        //is：改进可读性装饰器 ,底层is(equalTo(value))
        assertThat("zs",is("zs"));

        /**
         *  逻辑：
         */
        //allOf：所有匹配器都匹配才匹配,相当于 &&
        assertThat("张三", allOf(startsWith("张"), containsString("三")));
        //anyOf：任何匹配器匹配就匹配,相当于 ||
        assertThat("张三",anyOf(startsWith("李"),containsString("三")));
        // not：包装的匹配器不匹配器时匹配,相当于与取反
        assertThat("tom",not("lucy"));

        /**
         *  对象：
         */
        //equalTo：测试对象相等使用Object.equals方法
        assertThat("foo", equalTo("foo"));
        //hasToString：测试Object.toString方法
        assertThat(true, hasToString(equalTo("true")));
        //instanceOf, typeCompatibleWith：测试类型
        assertThat("string", instanceOf(String.class));
        assertThat(Integer.class, typeCompatibleWith(Number.class));
        //notNullValue, nullValue：测试null
        assertThat(null,nullValue());
        assertThat("",notNullValue());
        //sameInstance：测试对象实例
        Integer number = new Integer(200);
        assertThat(number,sameInstance(number));

        /**
         *  Beans：
         */
        @Data
        class MyClass{
            private String name;
        }
        //hasProperty：测试JavaBeans属性
        assertThat(new MyClass(),hasProperty("name"));

        /**
         *  集合：
         */
        //array：测试一个数组元素,每一项是否匹配
        assertThat(new Integer[]{1,2,3}, is(array(equalTo(1), equalTo(2), equalTo(3))));
        //hasEntry, hasKey, hasValue ：测试一个Map包含一个实体,键或者值
        Map<String,Integer> map = new HashMap<>();
        map.put("张三",23);
        map.put("李四",24);
        assertThat(map,hasEntry("张三",23));
        assertThat(map,hasKey("李四"));
        assertThat(map,hasValue(23));
        //hasItem, hasItems：测试一个集合包含一个元素
        assertThat(Arrays.asList("foo", "bar"),hasItem(startsWith("ba")));
        assertThat(Arrays.asList("foo", "bar", "baz"), hasItems(endsWith("z"), endsWith("o")));
        //hasItemInArray：测试一个数组包含一个元素
        assertThat(new String[] {"foo", "bar"}, hasItemInArray(startsWith("ba")));

        /**
         * 数字：
         */
        // closeTo：测试浮点值接近给定的值，该匹配器在+/-error范围内匹配
        assertThat(1.03, is(closeTo(1.0, 0.04)));
        //greaterThan, greaterThanOrEqualTo, lessThan, lessThanOrEqualTo ：测试次序
        assertThat(2, greaterThan(1));
        assertThat(1, greaterThanOrEqualTo(1));
        assertThat(1, lessThan(2));
        assertThat(1, lessThanOrEqualTo(1));

        /**
         * 文本：
         */
        //equalToIgnoringCase：测试字符串相等忽略大小写
        assertThat("Foo", equalToIgnoringCase("FOO"));
        //equalToIgnoringWhiteSpace：测试字符串忽略空白
        assertThat("   my\tfoo  bar ", equalToIgnoringWhiteSpace(" my  foo bar"));
        //containsString, endsWith, startsWith：测试字符串匹配
        assertThat("myStringOfNote", containsString("ring"));
        assertThat("myStringOfNote", endsWith("Note"));
        assertThat("myStringOfNote", startsWith("my"));

    }

三、自定义匹配器

示例代码：

import org.hamcrest.Description;
import org.hamcrest.Matcher;
import org.hamcrest.TypeSafeMatcher;

/**
 * 自定义匹配器,判断年龄范围在[1,200]返回true
 * 1、继承TypeSafeMatcher并指定泛型
 * 2、重写matchesSafely、describeTo方法
 * 3、提供外部调用的静态方法
 */
public class IsNormalAgeRange extends TypeSafeMatcher<Integer> {

    @Override
    public boolean matchesSafely(Integer number) {
        return number >=1 && number <=200;
    }
    
    @Override
    public void describeTo(Description description) {
        description.appendText("need to be within [1,200]");
    }

    public static Matcher normalAgeRange() {
        return new IsNormalAgeRange();
    }

}

测试：

    @Test
    public void testMyMatcher() {
        assertThat(100, IsNormalAgeRange.normalAgeRange());
    }