使用Lombok @Data时Jacoco未完全覆盖equals/hashCode的原因排查

你当前的测试用例遗漏了Lombok生成的equals和hashCode方法的几个关键分支场景，以下是具体缺失的测试点及补充方案：

缺失的测试场景 #

Equals方法未覆盖分支 #

1. 对象与自身比较：equals方法首先会判断this == obj，这一分支未被测试
2. 与null对象比较：equals方法会处理传入null的情况，需验证返回false
3. 与不同类实例比较：比如传入普通Object实例，需验证返回false
4. 字段为null的情况：当前测试所有字段均为非null值，需测试字段为null时的equals逻辑（如一个对象buildingId为null，另一个相同；或一个null一个非null）

HashCode方法未覆盖分支 #

1. 字段为null时的hashCode生成：需验证包含null字段的对象能正确生成hashCode，且相同null字段的对象hashCode一致

补充后的测试用例 #

import static org.junit.jupiter.api.Assertions.*;

import org.junit.jupiter.api.Test;

public class ModelTest {
    
    @Test
    void instantiateBuilding2ModelTest(){
        // Given
        String buildingId = "mail@mail.com";
        String buildingName ="myBuildingName";
        String buildingId2 = "secondmail@mail.com";
        String buildingName2 = "secondBuildingName";
        String buildinId3 = "thirdmail@mail.com";
        String buildingName3 = "thirdBuildingName";
        Building2 building2;
        Building2 building2_2 = new Building2(buildingId2, buildingName2);
        Building2 building2_3 = new Building2(buildinId3, buildingName3);
        

        // Test Getter
        building2 = new Building2(buildingId, buildingName);
        assertEquals(building2.getBuildingId(), buildingId);
        assertEquals(building2.getBuildingName(), buildingName);

        // Test Setter
        building2.setBuildingId(buildingId2);
        building2.setBuildingName(buildingName2);
        assertEquals(building2.getBuildingId(), buildingId2);
        assertEquals(building2.getBuildingName(), buildingName2);

        // Test toString
        String building2ToString = "Building2(buildingId=" + building2.getBuildingId() + ", buildingName=" + building2.getBuildingName() + ")";
        assertEquals(building2.toString(), building2ToString);

        // Test canEqual
        assertTrue(building2.canEqual(building2_3) && building2_3.canEqual(building2));

        // Test equals
        assertTrue(building2.equals(building2_2));
        assertFalse(building2.equals(building2_3));
        
        // 补充equals测试场景
        // 1. 自身比较
        assertTrue(building2.equals(building2));
        // 2. 与null比较
        assertFalse(building2.equals(null));
        // 3. 与不同类实例比较
        assertFalse(building2.equals(new Object()));
        // 4. 字段为null的情况
        Building2 nullIdBuilding = new Building2(null, buildingName2);
        Building2 sameNullIdBuilding = new Building2(null, buildingName2);
        Building2 nullNameBuilding = new Building2(buildingId2, null);
        assertTrue(nullIdBuilding.equals(sameNullIdBuilding));
        assertFalse(building2.equals(nullIdBuilding));
        assertFalse(nullIdBuilding.equals(nullNameBuilding));

        // Test hashCode
        assertTrue(building2.hashCode() == building2_2.hashCode());
        assertFalse(building2.hashCode() == building2_3.hashCode());
        
        // 补充hashCode测试场景
        // 字段为null时的hashCode
        assertTrue(nullIdBuilding.hashCode() == sameNullIdBuilding.hashCode());
        // 自身hashCode一致
        int originalHashCode = building2.hashCode();
        assertEquals(originalHashCode, building2.hashCode());
    }
}

说明 #

Lombok生成的equals方法严格遵循Java规范处理所有边界情况，Jacoco会检测这些分支是否被执行。补充上述测试后，equals和hashCode的所有分支将被完全覆盖。

内容的提问来源于stack exchange，提问作者Robin Joseph