Mockito无法Mock任何对象求助：Mock集合类均报错

我是单元测试新手，尝试用Mockito Mock一个Map，结果Mock ConcurrentHashMap时出错，而且所有对象都Mock失败。

测试代码 #

import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

import java.util.concurrent.ConcurrentHashMap;

import static org.mockito.Mockito.mock;

class UtilsTest {


    @BeforeEach
    void setUp() {
        ConcurrentHashMap mockedMap = mock(ConcurrentHashMap.class);
    }

    @Test
    void lessLoadedServersCount(){

    }
}

报错信息 #

JDK 11下的报错 #

org.mockito.exceptions.base.MockitoException: 
Mockito cannot mock this class: class java.util.concurrent.ConcurrentHashMap.

Mockito can only non-private & non-final classes.
If you're not sure why you're getting this error, please report to the mailing list.


Java               : 11
JVM vendor name    : OpenLogic
JVM vendor version : 11.0.19+7-adhoc.admin.jdk11u
JVM name           : OpenJDK 64-Bit Server VM
JVM version        : 11.0.19+7-adhoc.admin.jdk11u
JVM info           : mixed mode
OS name            : Mac OS X
OS version         : 13.2.1



Underlying exception : java.lang.UnsupportedOperationException: Cannot define class using reflection: Could not find sun.misc.Unsafe

更换为JDK 19后的报错 #

Mock ArrayList时：

org.mockito.exceptions.base.MockitoException: 
Mockito cannot mock this class: class java.util.ArrayList.

Mockito can only non-private & non-final classes.
If you're not sure why you're getting this error, please report to the mailing list.

Mock HashSet时：

org.mockito.exceptions.base.MockitoException: 
Mockito cannot mock this class: class java.util.HashSet.

Mockito can only non-private & non-final classes.
If you're not sure why you're getting this error, please report to the mailing list.

• 检查Mockito版本兼容性
  确保Mockito版本与JDK版本匹配：JDK 11+需用Mockito 3.3.0及以上，JDK 19需用Mockito 4.5.0及以上。更新依赖示例：
  Maven：

  <dependency>
      <groupId>org.mockito</groupId>
      <artifactId>mockito-core</artifactId>
      <version>4.11.0</version>
      <scope>test</scope>
  </dependency>
  <dependency>
      <groupId>org.mockito</groupId>
      <artifactId>mockito-junit-jupiter</artifactId>
      <version>4.11.0</version>
      <scope>test</scope>
  </dependency>
  

  Gradle：

  testImplementation 'org.mockito:mockito-core:4.11.0'
  testImplementation 'org.mockito:mockito-junit-jupiter:4.11.0'
  

• 优先Mock接口而非具体类
  不要直接MockConcurrentHashMap、ArrayList这类具体类，改为Mock它们的接口Map、List、Set，既符合面向接口原则，也能规避Mockito对具体类的Mock限制：

  Map<String, Object> mockedMap = mock(Map.class);
  List<String> mockedList = mock(List.class);
  Set<String> mockedSet = mock(Set.class);
  

• 添加Mockito-inline依赖（针对必须Mock具体类的场景）
  如果确实需要Mock具体类，添加mockito-inline依赖，它支持Mock final类、静态方法，解决JDK模块系统带来的限制：
  Maven：

  <dependency>
      <groupId>org.mockito</groupId>
      <artifactId>mockito-inline</artifactId>
      <version>4.11.0</version>
      <scope>test</scope>
  </dependency>
  

  Gradle：

  testImplementation 'org.mockito:mockito-inline:4.11.0'
  

• 配置JVM参数
  针对JDK 9+，在测试运行配置中添加--add-opens java.base/java.util=ALL-UNNAMED参数，确保Mockito能访问java.util包的内部类。

内容的提问来源于stack exchange，提问作者MohanaSundaram J