return ResponseEntity.status(HttpStatus.OK).body(result);

Required request body is missing

def "Signup"() {
        given:
            UserDto userDto = new UserDto(id: 1, password: "password123",   username: "username123")
            def personDto = new PersonDto(id: 1, user : userDto)
        when: "signup url is hit"
            def response = mockMvc.perform(post('/person/signup'))
        then:
            applicantService.signup(userDto) >> personDto
            response.andExpect(status().isOk())
    }