Spring Boot中Mockito测试抛出异常失败问题排查及测试建议

问题背景 #

作为Spring Boot新手，尝试测试服务类在保存失败时是否会正确处理IllegalArgumentException，但始终无法触发异常场景，测试方法2返回状态码201而非预期的500。

服务类代码片段 #

public ResponseEntity<ModelApiResponse> createResponse(Response response)
        throws JsonProcessingException, IllegalArgumentException{
    try{
        chatResponseRepository.save(response);

        return new ResponseEntity<>(HttpStatus.valueOf(GlobalVariables.RESPONSE_CODE_201));
    } catch (IllegalArgumentException ex){
        return new ResponseEntity<>(HttpStatus.valueOf(GlobalVariables.RESPONSE_CODE_500));
    }
}

两种测试方法及问题 #

测试方法1 #

@Test
public void testThatResponseCreationThrowsErrorWhenSavingFails() throws Exception{
    Response responseMock = mock(Response.class);
    when(chatResponseRepositoryMock.save(new Response())).thenThrow(IllegalArgumentException.class);

    assertThrows(IllegalArgumentException.class, () -> abbyResponseRepositoryMock.save(abbyResponseMock));
}

问题：该测试完全偏离目标——直接调用Mock仓库的save方法，根本没触发服务类的createResponse逻辑，服务类的try-catch处理完全没被执行，也验证不了服务类的异常处理行为。

测试方法2 #

@Test
public void testThatResponseCreationThrowsErrorWhenSavingFails() throws Exception {
    Mockito.when(chatResponseRepositoryMock.save(new Response())).thenThrow(Mockito.mock(IllegalArgumentException.class));

    Response response = new Response();
    response.setMessage("This is a unit test response message");
    response.setNxtMessageId("98765");

    mockMvc.perform(post("/api/v1/responses/create-response")
            .header(HttpHeaders.AUTHORIZATION, "Basic " + "credentials")
            .header(GlobalVariables.X_CORRELATION_ID, "123456")
            .header(GlobalVariables.X_SOURCE_APP, "source_app")
            .header(GlobalVariables.X_USER, "user")
            .header(GlobalVariables.X_USER_ROLE, "user")
            .content(this.json(response))
            .contentType(contentType))
            .andExpect(jsonPath("$.header.responseCode", is(500)))
            .andExpect(jsonPath("$.header.responseMessage", is("Error saving chat response")))
            .andReturn();
}

测试结果：

Expected: is <500>
     but: was <201>

问题：Mockito的匹配条件用了save(new Response())，这要求传入的对象和new Response()是同一个实例，但实际测试中传入的是自定义了message和nxtMessageId的Response对象，实例不匹配，导致Mock的异常抛出逻辑未触发，仓库执行默认Mock行为，服务类走正常流程返回201。

解决方案 #

修正测试方法1（服务类单元测试） #

调整Mock匹配规则为任意Response实例，同时断言服务类返回的状态码（注意服务类已捕获异常，不会向外抛出）：

@Test
public void testThatResponseCreationReturns500WhenSavingFails() throws Exception{
    // 匹配任意Response实例，触发异常
    when(chatResponseRepositoryMock.save(any(Response.class))).thenThrow(IllegalArgumentException.class);
    
    // 调用服务类核心方法
    ResponseEntity<ModelApiResponse> result = yourService.createResponse(new Response());
    
    // 断言返回状态码为500
    assertEquals(HttpStatus.valueOf(GlobalVariables.RESPONSE_CODE_500), result.getStatusCode());
}

修正测试方法2（控制器集成测试） #

同样修改Mock的匹配规则为任意Response实例，同时确保服务类返回的ResponseEntity包含正确的ModelApiResponse对象（否则jsonPath断言会失败）：

@Test
public void testThatCreateResponseEndpointReturns500WhenSavingFails() throws Exception {
    // 匹配任意Response实例，触发异常
    Mockito.when(chatResponseRepositoryMock.save(any(Response.class))).thenThrow(IllegalArgumentException.class);

    Response response = new Response();
    response.setMessage("This is a unit test response message");
    response.setNxtMessageId("98765");

    mockMvc.perform(post("/api/v1/responses/create-response")
            .header(HttpHeaders.AUTHORIZATION, "Basic " + "credentials")
            .header(GlobalVariables.X_CORRELATION_ID, "123456")
            .header(GlobalVariables.X_SOURCE_APP, "source_app")
            .header(GlobalVariables.X_USER, "user")
            .header(GlobalVariables.X_USER_ROLE, "user")
            .content(this.json(response))
            .contentType(contentType))
            .andExpect(status().is(500))
            .andExpect(jsonPath("$.header.responseCode", is(500)))
            .andExpect(jsonPath("$.header.responseMessage", is("Error saving chat response")))
            .andReturn();
}

额外注意：服务类的catch块需要正确构造包含header信息的ModelApiResponse对象，否则响应体为空，jsonPath断言会失败，例如：

catch (IllegalArgumentException ex){
    ModelApiResponse errorResponse = new ModelApiResponse();
    errorResponse.setHeader(new ResponseHeader(500, "Error saving chat response"));
    return new ResponseEntity<>(errorResponse, HttpStatus.valueOf(GlobalVariables.RESPONSE_CODE_500));
}

测试方法选型建议 #

• 测试方法1（单元测试）：更适合单独验证服务类的核心逻辑，速度快，能精准覆盖服务层的异常处理、状态码返回等逻辑，是日常开发中优先编写的测试用例。
• 测试方法2（集成测试）：用于验证从HTTP请求到控制器、服务、仓库的完整流程，确保端到端的请求响应符合业务预期，适合作为补充测试，覆盖接口级别的场景。

内容的提问来源于stack exchange，提问作者Kibet Kyle