Spring Boot中RestController单元测试when方法报错求助

问题场景 #

编写Spring Boot的RestController单元测试时，listBook接口的测试代码执行报错，核心是请求参数构建环节误用Mockito匹配器，导致接口执行异常，断言失败。

RestController方法 #

@GetMapping("/search")
public ResponseEntity<List<BookResponse>> listBook(@RequestParam(name = "size") int size, @RequestParam(name = "page") int page) {
    final Long userID = userService.findInContextUser().getId();
    return ResponseEntity.ok(bookListService.listBooks(size, page, userID));
}

原错误测试代码 #

@Test
void itShouldGetBooks_WhenSearch() throws Exception {

    // given - precondition or setup
    BookResponse response1 = BookResponse.builder()
            .title("Book 1")
            .authorName("authorName")
            .build();

    BookResponse response2 = BookResponse.builder()
            .title("Book 1")
            .authorName("authorName2")
            .build();

    List<BookResponse> response = List.of(response1, response2);

    UserDto userDto = UserDto.builder()
            .id(1L)
            .username("username")
            .build();

    // when -  action or the behaviour that we are going test
    when(userService.findInContextUser()).thenReturn(userDto);
    when(bookListService.listBooks(anyInt(), anyInt(), eq(userDto.getId()))).thenReturn(response);

    // then - verify the output
    mockMvc.perform(get("/api/v1/book/search?size=" + anyInt() + "&page=" + anyInt()) // 错误行
                    .contentType(MediaType.APPLICATION_JSON))
            .andDo(print())
            .andExpect(jsonPath("$", hasSize(2))) // 断言失败行
            .andExpect(status().isOk());
}

报错信息 #

java.lang.AssertionError: JSON path "$"
Expected: a collection with size <2>
     but: was LinkedHashMap <{error=Request processing failed; nested exception is org.mockito.exceptions.misusing.InvalidUseOfMatchersException: 
Invalid use of argument matchers!
0 matchers expected, 2 recorded:

错误原因 #

1. Mockito匹配器误用：anyInt()是Mockito专属的参数匹配器，仅能在when()或verify()等Mockito方法上下文中使用，不能直接拼接到URL字符串作为请求参数。这种错误用法触发了InvalidUseOfMatchersException。
2. 接口执行异常：参数错误导致接口内部抛出异常，返回的是错误信息的LinkedHashMap，而非预期的BookResponse列表，因此jsonPath("$", hasSize(2))断言失败。

修复方案 #

核心修复点 #

将URL中错误使用的anyInt()替换为具体整数，并改用.param()方法构建请求参数（更规范）。Mockito的when()配置本身是正确的，无需修改。

修复后的完整测试代码 #

@Test
void itShouldGetBooks_WhenSearch() throws Exception {

    // given - precondition or setup
    BookResponse response1 = BookResponse.builder()
            .title("Book 1")
            .authorName("authorName")
            .build();

    BookResponse response2 = BookResponse.builder()
            .title("Book 1")
            .authorName("authorName2")
            .build();

    List<BookResponse> response = List.of(response1, response2);

    UserDto userDto = UserDto.builder()
            .id(1L)
            .username("username")
            .build();

    // when -  action or the behaviour that we are going test
    when(userService.findInContextUser()).thenReturn(userDto);
    when(bookListService.listBooks(anyInt(), anyInt(), eq(userDto.getId()))).thenReturn(response);

    // then - verify the output
    mockMvc.perform(get("/api/v1/book/search")
                    .param("size", "10") // 使用具体数值作为参数
                    .param("page", "0")
                    .contentType(MediaType.APPLICATION_JSON))
            .andDo(print())
            .andExpect(jsonPath("$", hasSize(2)))
            .andExpect(status().isOk());
}

额外优化建议 #

• 用.param()方法添加请求参数，比直接拼接URL更清晰，避免字符串拼接错误。
• 若需测试多组size和page值，可使用@ParameterizedTest实现参数化测试，覆盖更多场景。

内容的提问来源于stack exchange，提问作者Sercan Noyan Germiyanoğlu