testing excel-file download by request

 MvcRequester.on(mockMvc)
             .to("/api/reports/complaints/full")                                        
             .get()
             .doExpect(status().isOk())
             .returnAs(MultipartFile.class); //drop here, tried to use File, InputStream, FileInputStream

I this is the part of the test that makes sending the request to the endpoint. An excel file comes from this endpoint. Please tell me how to write the response into a variable.
here is response body and exception.
I use custom library for inject file into response. It's work correct 100%.

Here is end of controller method with adding file into response

@GetMapping("/complaints/full")
    @ResponseBody
    public void getComplaintsFullReport(SearchComplaintDto dto,
                                        HttpServletResponse servletResponse) {

        SearchComplaintArgument argument = complaintMapper.toSearchArgument(dto);

        File file = buildComplaintsReportAction.execute(argument);
        FileResponse.builder()
                    .file(file)
                    .filename("Report_"
                                      .concat(LocalDateTime.now().format(DateTimeFormatter.ofPattern("dd.MM.yyyy_HH.mm")))
                                      .concat(".xlsx"))
                    .mimeType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
                    .response(servletResponse)
                    .build();
    }

Answer to the question "How can i write the response into a variable?".

        byte[] response = MvcRequester.on(mockMvc)
                                  .to("/api/reports/complaints/full")
                                  .get()
                                  .doExpect(status().isOk())
                                  .returnResponse()
                                  .getContentAsByteArray();

change dependency to (before i used not this dependency, it was custom dependency with same appointment)

   <dependency>
        <groupId>com.jupiter-tools</groupId>
        <artifactId>mvc-requester</artifactId>
        <version>0.4</version>
        <scope>test</scope>
    </dependency>

Then i got response as byte array, i can compare it with expected file as i wish.