#vulnerable code 
                                @Test
    public void testPostMultipleFiles() throws JSONException, URISyntaxException {
        HttpResponse<JsonNode> response = Unirest.post("http://httpbin.org/post").field("param3", "wot").field("file1", new File(getClass().getResource("/test").toURI())).field("file2", new File(getClass().getResource("/test").toURI())).asJson();

        JSONObject names = response.getBody().getObject().getJSONObject("files");
        assertEquals(2, names.length());

        assertEquals("This is a test file", names.getString("file1"));
        assertEquals("This is a test file", names.getString("file2"));

        assertEquals("wot", response.getBody().getObject().getJSONObject("form").getString("param3"));
    } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testPostMultipleFiles() throws JSONException, URISyntaxException {
        HttpResponse<JsonNode> response = Unirest.post(MockServer.POST)
                .field("param3", "wot")
                .field("file1", new File(getClass().getResource("/test").toURI()))
                .field("file2", new File(getClass().getResource("/test").toURI()))
                .asJson();

        parse(response)
                .assertParam("param3", "wot")
                .assertFileContent("file1", "This is a test file")
                .assertFileContent("file2", "This is a test file");
    }