如何为含Lambda表达式的Spring Security配置编写Mockito单元测试

问题背景 #

你需要为Spring Security配置类中返回Lambda实现的authoritiesMapper() Bean编写单元测试，但现有测试无法覆盖Lambda内的代码。

原Bean方法代码 #

@Bean
public GrantedAuthoritiesMapper authoritiesMapper() {
    return (authorities) -> {
        Set<GrantedAuthority> mappedAuthorities = new HashSet<>();

        authorities.forEach(authority -> {
           if (OAuth2UserAuthority.class.isInstance(authority)) {
                OAuth2UserAuthority oauth2UserAuthority = (OAuth2UserAuthority)authority;

                Map<String, Object> userAttributes = oauth2UserAuthority.getAttributes();

                ((List<String>) userAttributes.getOrDefault("field", List.of())).forEach(a-> mappedAuthorities.add( new SimpleGrantedAuthority(a)));
            }
        });
        return mappedAuthorities;
    };
}

现有未覆盖代码的测试 #

@Before
public void setUp() {
    this.config = new Config(); // Config类包含authoritiesMapper方法
}

@Test
public void testMapper(){
    this.config.authoritiesMapper();
}

问题原因 #

你的测试仅调用了authoritiesMapper()方法获取GrantedAuthoritiesMapper实例，但Lambda表达式的逻辑只会在该实例的mapAuthorities()方法（GrantedAuthoritiesMapper接口的核心方法）被调用时执行。现有测试完全没触发这个方法，自然无法覆盖Lambda内的代码。

解决方案 #

直接构造测试用的权限集合，调用GrantedAuthoritiesMapper的mapAuthorities()方法，验证输出结果即可。这个场景无需Mockito，手动构造测试对象更直接。

完整测试示例 #

import org.junit.Before;
import org.junit.Test;
import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.authority.SimpleGrantedAuthority;
import org.springframework.security.oauth2.core.user.OAuth2UserAuthority;

import java.util.*;

import static org.junit.Assert.*;

public class ConfigTest {

    private Config config;
    private GrantedAuthoritiesMapper authoritiesMapper;

    @Before
    public void setUp() {
        config = new Config();
        authoritiesMapper = config.authoritiesMapper(); // 获取Mapper实例
    }

    @Test
    public void testAuthoritiesMapper_WithOAuth2UserAuthority() {
        // 1. 构造带目标属性的OAuth2UserAuthority
        Map<String, Object> userAttributes = new HashMap<>();
        userAttributes.put("field", Arrays.asList("ROLE_USER", "ROLE_ADMIN"));
        OAuth2UserAuthority oauth2Authority = new OAuth2UserAuthority(userAttributes);

        // 2. 构造输入权限集合
        Collection<? extends GrantedAuthority> inputAuthorities = Collections.singletonList(oauth2Authority);

        // 3. 调用mapAuthorities触发Lambda逻辑
        Collection<? extends GrantedAuthority> result = authoritiesMapper.mapAuthorities(inputAuthorities);

        // 4. 验证结果
        assertEquals(2, result.size());
        assertTrue(result.contains(new SimpleGrantedAuthority("ROLE_USER")));
        assertTrue(result.contains(new SimpleGrantedAuthority("ROLE_ADMIN")));
    }

    @Test
    public void testAuthoritiesMapper_WithoutOAuth2UserAuthority() {
        // 构造普通权限，验证不会被处理
        Collection<? extends GrantedAuthority> inputAuthorities = Collections.singletonList(new SimpleGrantedAuthority("ROLE_GUEST"));

        Collection<? extends GrantedAuthority> result = authoritiesMapper.mapAuthorities(inputAuthorities);

        assertTrue(result.isEmpty());
    }

    @Test
    public void testAuthoritiesMapper_NoFieldAttribute() {
        // 构造无目标属性的OAuth2UserAuthority
        Map<String, Object> userAttributes = new HashMap<>();
        OAuth2UserAuthority oauth2Authority = new OAuth2UserAuthority(userAttributes);
        Collection<? extends GrantedAuthority> inputAuthorities = Collections.singletonList(oauth2Authority);

        Collection<? extends GrantedAuthority> result = authoritiesMapper.mapAuthorities(inputAuthorities);

        assertTrue(result.isEmpty());
    }
}

关键要点 #

• 必须触发Lambda对应的接口方法：不要只调用获取Bean的方法，一定要调用mapAuthorities()才能执行Lambda内的逻辑
• 覆盖多场景测试：包含目标属性的OAuth2权限、普通权限、无目标属性的OAuth2权限，确保所有逻辑分支都被覆盖
• 优先手动构造测试对象：这个场景无需Mockito，直接构造测试用例更简洁；若有复杂依赖再结合Mockito使用

内容的提问来源于stack exchange，提问作者XAJA