前言

Hamcrest是用于Java的单元测试的框架，它使用matcher匹配器来进行断言。在Spring-boot-starter中集成了Hamcrest,无需而外引入。

核心API

1. is

• 使用is匹配器使得程序更加易懂

String str1 = "text";
String str2 = " text ";
assertThat(str1, is(equalToIgnoringWhiteSpace(str2)));

• 用于简单数据类型的判断

String str1 = "text";
String str2 = "text";
assertThat(str1, is(str2));

2. not
   和is使用方式一样，只是含义相反。

• 使用not匹配器使得程序更加易懂

String str1 = "text";
String str2 = " text ";
assertThat(str1, not(equalToIgnoringWhiteSpace(str2)));

• 用于简单数据类型的判断

String str1 = "text";
String str2 = "text";
assertThat(str1, not(str2));

3. containsString
   是否包含子串

String str1 = "text123";
String str2 = "text";
assertThat(str1, containsString(str2));

4. 以为某个字段开头/结尾

String str1 = "text123";
assertThat(str1, startsWith("text"));// 以某个字符开头
assertThat(str1, endsWith("text"));// 以某个字符开头

5. 判断两个对象是否为同一个实体

Cat cat=new Cat();
assertThat(cat, sameInstance(cat));

6. 类似OR的效果

String str = "calligraphy";
String start = "call";
String end = "foo";
assertThat(str, anyOf(startsWith(start), containsString(end)));

7. 类似AND的效果

String str = "calligraphy";
String start = "call";
String end = "phy";
assertThat(str, allOf(startsWith(start), endsWith(end)));

匹配器

Number 匹配器

assertThat(1, greaterThan(0)); // 大于
assertThat(5, greaterThanOrEqualTo(5)); //大于等于
assertThat(-1, lessThan(0)); // 小于
assertThat(-1, lessThanOrEqualTo(5)); // 小于等于

Text 匹配器

1. 匹配空串

String str = "";
assertThat(str, isEmptyString()); // 空字符串
assertThat(str, isEmptyOrNullString()); // 空字符串或者null

2. 匹配字符串相等

String str1 = "text";
String str2 = " text ";
assertThat(str1, equalToIgnoringWhiteSpace(str2)); // 忽略左右空白
assertThat(a, equalToIgnoringCase(b)); //忽略大小写

Collections 匹配器

1. 检查某个元素是否在集合中

List<String> collection = Lists.newArrayList("ab","cd","ef");
assertThat(collection, hasItem("cd"));
assertThat(collection, not(hasItem("zz")));
assertThat(collection, hasItems("cd", "ab")); // 检查多个元素是否在集合中

2. 检查所有元素

List<String> collection = Lists.newArrayList("ab","cd","ef");
assertThat(collection, hasItems("ab","cd","ef"));
assertThat(collection, hasItems("cd", "ab","ef")); // 错误
assertThat(collection, hasItems("ab","cd")); // 错误
assertThat(collection, containsInAnyOrder("cd", "ab","ef")); //正确,不区分顺序

3. 为空检查

• 集合为空检查

List<String> collection = Lists.newArrayList("ab","cd","ef");
assertThat(collection, empty()); // false, 用于检查集合类型

• 数组为空检查

String[] array = new String[] { "ab" };
assertThat(array, emptyArray()); // false

• map为空检查

Map<String, String> maps = Maps.newHashMap();
assertThat(maps, equalTo(Collections.EMPTY_MAP));

• Iterable为空检查

Iterable<String> collection = Lists.newArrayList();
assertThat(collection, emptyIterable());

4. 检查数目

• 检查集合数目

List<String> list = Lists.newArrayList("ab", "cd", "ef");
assertThat(list, hasSize(3));

• 检查iterable数目

Iterable<String> list = Lists.newArrayList("ab", "cd", "ef");
assertThat(list, iterableWithSize(3));

5. 检查每项的条件

List<String> list = Lists.newArrayList("ab", "cd", "ef");
assertThat(list, everyItem(equalTo("ab")));

Bean 匹配器

定义一个City的bean

@Data
@AllArgsConstructor
public class City {
    String name;
    String state;
}

1. 测试是否存在某个属性

City city = new City("shenzhen", "CA");
assertThat(city, hasProperty("state"));
assertThat(city, hasProperty("state", equalTo("CA"))); // 判断是否存在某个属性，并且是否存在某个特性值

2. 判断两个对象property值是否一样

City city = new City("San Francisco", "CA");
City city2 = new City("San Francisco", "CA");
assertThat(city, samePropertyValuesAs(city2));

refer

https://www.baeldung.com/java-junit-hamcrest-guide