@RequestBody List<MultipartFile> documents integration test

I can't figure out why my List documents is always null

That's Controller code

@PostMapping(value = "/{documentType}/list", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    public ResponseEntity<Void> uploadListOfDocuments(@ApiParam(hidden = true) @RequestAttribute(SharedConstants.USER_ID_ATTRIBUTE) Long userId,
                                                      @PathVariable DocumentType documentType,
                                                      @RequestBody List<MultipartFile> documents) {
        documentGatewayService.uploadListOfDocuments(documents, documentType, userId);
        return ResponseEntity.ok().build();
    }

That's integration test

@Test
    void uploadListOfDocuments() throws Exception {
        MockMultipartFile firstFile = new MockMultipartFile("data", "filename.txt", String.valueOf(MediaType.MULTIPART_FORM_DATA), "some xml".getBytes());
        MockMultipartFile secondFile = new MockMultipartFile("data", "other-file-name.data", String.valueOf(MediaType.MULTIPART_FORM_DATA), "some other type".getBytes());
        MockMultipartFile jsonFile = new MockMultipartFile("json", "", String.valueOf(MediaType.MULTIPART_FORM_DATA), "{\"json\": \"someValue\"}".getBytes());

        mockMvc.perform(
                        multipart("/document/{documentType}/list", "PASSPORT")
                                .file(firstFile)
                                .file(secondFile)
                                .file(jsonFile)
                                .content(firstFile.getBytes())
                                .content(secondFile.getBytes())
                                .content(jsonFile.getBytes())
                                .requestAttr(SharedConstants.USER_ID_ATTRIBUTE, 1L)
                        )
                .andExpect(status().isOk());
    }

I tried many options, but still got null. I would be grateful if anyone could help me figure it out.

The names of MockMultipartFile objects at your tests have to be equal to the name of List<MultipartFile> request parameter

In your case they should look like

MockMultipartFile firstFile = new MockMultipartFile("documents", "filename.txt", String.valueOf(MediaType.MULTIPART_FORM_DATA), "some xml".getBytes());
MockMultipartFile secondFile = new MockMultipartFile("documents", "other-file-name.data", String.valueOf(MediaType.MULTIPART_FORM_DATA), "some other type".getBytes());
// ...