creatUser.java

     public void creatUser() 
     {
        String url = "http://localhost:" + port + "/users";

        String username = "chathuranga";
        String password = "123";

        HttpHeaders requestHeaders = new HttpHeaders();
        requestHeaders.setContentType(MediaType.APPLICATION_JSON);
        requestHeaders.setAccept(Arrays.asList(MediaType.APPLICATION_JSON));


        AddUserRequest addUserRequest = new AddUserRequest();
        addUserRequest.setName("Sample User");
        addUserRequest.setUsername("user1");
        addUserRequest.setPassword("pass123");

        HttpEntity<AddUserRequest> requestEntity = new HttpEntity<>(addUserRequest, requestHeaders);

        //basic authentication is made with  'withBasicAuth' method available in the TestRestTemplate
        ResponseEntity<AddUserResponse> responseEntity = testRestTemplate.withBasicAuth(username, password)
                .exchange(
                        url,
                        HttpMethod.POST,
                        requestEntity,
                        AddUserResponse.class
                );

        if (responseEntity.getStatusCode() == HttpStatus.OK) 
        {
            AddUserResponse addUserResponse = responseEntity.getBody();
            System.out.println(addUserResponse);
        }
    }