How do I mock a REST template exchange

Question

I have a service in which I need to ask an outside server via rest for some information   public class SomeService        public List lt ObjectA gt  getListofObjectsA             List lt ObjectA gt  objectAList   new ArrayList lt ObjectA gt             ParameterizedTypeReference lt List lt ObjectA gt  gt  typeRef   new ParameterizedTypeReference lt List lt ObjectA gt  gt                ResponseEntity lt List lt ObjectA gt  gt  responseEntity   restTemplate exchange   objects get-objectA   HttpMethod POST  new HttpEntity lt  gt  ObjectAList   typeRef           return responseEntity getBody              How can I write a JUnit test for getListofObjectsA     I have tried with the below    RunWith MockitoJUnitRunner class  public class SomeServiceTest       private MockRestServiceServer mockServer        Mock     private RestTemplate restTemplate        Inject    private SomeService underTest    Before public void setup         mockServer   MockRestServiceServer createServer restTemplate       underTest   new SomeService restTemplate       mockServer expect requestTo   objects get-objectA    andExpect method HttpMethod POST                andRespond withSuccess   json list response    MediaType APPLICATION JSON            Test     public void testGetObjectAList         List lt ObjectA gt  res   underTest getListofObjectsA        Assert assertEquals myobjectA  res get 0        However the above code does not work  it shows that responseEntitty is null   How can I correct my test to properly mock restTemplate exchange

User · Answer

I implemented a small library that is quite useful  It provides a ClientHttpRequestFactory that can receive some context  By doing so  it allows to go through all client layers such as checking that query parameters are valued  headers set  and check that deserialization works well

User · Answer

If anyone has this problem while trying to mock restTemplate exchange       the problem seems to be with matchers  As an example  the following won t work  when ecocashRestTemplate exchange Mockito any                     Mockito eq HttpMethod GET                    Mockito any HttpEntity class                    Mockito  lt Class lt UserTransaction gt  gt any              thenReturn new ResponseEntity lt  gt  transaction  HttpStatus OK     but this one will actually work    ResponseEntity lt UserTransaction gt  variable   new ResponseEntity lt  gt  transaction  HttpStatus OK     when ecocashRestTemplate exchange Mockito anyString                     Mockito eq HttpMethod GET                    Mockito any HttpEntity class                    Mockito  lt Class lt UserTransaction gt  gt any         thenReturn new ResponseEntity lt  gt  transaction  HttpStatus OK     NOTICE the Mockito anyString   on the second block vs theMockito any

User · Answer

For me  I had to use Matchers any URI class    Mockito when restTemplate exchange Matchers any URI class   Matchers any HttpMethod class   Matchers  lt HttpEntity lt   gt  gt  any    Matchers  lt Class lt Object gt  gt  any     thenReturn myEntity

User · Answer

If anyone is still facing this issue  Captor annotation worked for me  Captor private ArgumentCaptor lt Object gt  argumentCaptor   Then I was able to mock the request by  ResponseEntity lt YourTestResponse gt  testEntity   new ResponseEntity lt  gt       getTestFactoryResponse         HttpStatus OK   when mockRestTemplate exchange  String  argumentCaptor capture          HttpMethod  argumentCaptor capture          HttpEntity lt   gt   argumentCaptor capture          Class lt YourTestResponse class gt   any      thenReturn testEntity

User · Answer

If you are using RestTemplateBuilder may be the usual thing wouldn t work  You need to add this in your test class along with when condition     Before     public void setup                  ReflectionTestUtils setField service   restTemplate   restTemplate

User · Answer

If your intention is test the service without care about the rest call  I will suggest to not use any annotation in your unit test to simplify the test   So  my suggestion is refactor your service to receive the resttemplate using injection constructor  This will facilitate the test  Example    Service class SomeService        AutoWired     SomeService TestTemplateObjects restTemplateObjects            this restTemplateObjects   restTemplateObjects            The RestTemplate as component  to be injected and mocked after    Component public class RestTemplateObjects        private final RestTemplate restTemplate       public RestTemplateObjects              this restTemplate   new RestTemplate               you can add extra setup the restTemplate here  like errorHandler or converters            public RestTemplate getRestTemplate             return restTemplate            And the test   public void test          when mockedRestTemplateObject get  thenReturn mockRestTemplate          mock restTemplate exchange     when mockRestTemplate exchange       thenReturn mockedResponseEntity        SomeService someService   new SomeService mockedRestTemplateObject       someService getListofObjectsA        In this way  you have direct access to mock the rest template by the SomeService constructor

User · Answer

The RestTemplate instance has to be a real object  It should work if you create a real instance of RestTemplate and make it  Spy    Spy private RestTemplate restTemplate   new RestTemplate

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Let say you have an exchange call like below   String url     zzz  accountNumber     Optional lt AccountResponse gt  accResponse   Optional ofNullable accountNumber           map account - gt                  HttpHeaders headers   new HttpHeaders                headers setContentType MediaType APPLICATION JSON               headers set  Authorization    bearer 121212                  HttpEntity lt Object gt  entity   new HttpEntity lt  gt  headers               ResponseEntity lt AccountResponse gt  response   template exchange                      url                      GET                      entity                      AccountResponse class                      accountNumber                             return response getBody                   To mock this in your test case you can use mocitko as below   when restTemplate exchange          ArgumentMatchers anyString            ArgumentMatchers any HttpMethod class           ArgumentMatchers any            ArgumentMatchers  lt Class lt AccountResponse gt  gt any            ArgumentMatchers  lt ParameterizedTypeReference lt List lt Object gt  gt  gt any

User · Answer

This work on my side   ResourceBean resourceBean   initResourceBean    ResponseEntity lt ResourceBean gt  responseEntity         new ResponseEntity lt ResourceBean gt  resourceBean  HttpStatus ACCEPTED   when restTemplate exchange      Matchers anyObject         Matchers any HttpMethod class       Matchers  lt HttpEntity gt  any         Matchers  lt Class lt ResourceBean gt  gt  any       thenReturn responseEntity

User · Answer

I used to get such an error  I found a more reliable solution  I have mentioned the import statements too which have worked for me  The below piece of code perfectly mocks restemplate   import org mockito Matchers  import static org mockito Matchers any       HttpHeaders headers   new Headers        headers setExpires 10000L            ResponseEntity lt String gt  responseEntity   new ResponseEntity lt  gt   dummyString   headers  HttpStatus OK       when restTemplate exchange  Matchers anyString                 Matchers any HttpMethod class               Matchers  lt HttpEntity lt   gt  gt  any                 Matchers  lt Class lt String gt  gt  any     thenReturn responseEntity

User · Answer

ResponseEntity lt String gt  responseEntity   new ResponseEntity lt String gt   sampleBodyString   HttpStatus ACCEPTED   when restTemplate exchange                             Matchers anyString                                Matchers any HttpMethod class                              Matchers  lt HttpEntity lt   gt  gt  any                                Matchers  lt Class lt String gt  gt  any                                                          thenReturn responseEntity

User · Answer

This is an example with the non deprecated ArgumentMatchers class  when restTemplate exchange                  ArgumentMatchers anyString                    ArgumentMatchers any HttpMethod class                   ArgumentMatchers any                    ArgumentMatchers  lt Class lt String gt  gt any                   thenReturn responseEntity

User · Answer

You don t need MockRestServiceServer object  The annotation is  InjectMocks not  Inject  Below is an example code that should work   RunWith MockitoJUnitRunner class  public class SomeServiceTest        Mock     private RestTemplate restTemplate        InjectMocks     private SomeService underTest        Test     public void testGetObjectAList             ObjectA myobjectA   new ObjectA              define the entity you want the exchange to return         ResponseEntity lt List lt ObjectA gt  gt  myEntity   new ResponseEntity lt List lt ObjectA gt  gt  HttpStatus ACCEPTED           Mockito when restTemplate exchange              Matchers eq   objects get-objectA                Matchers eq HttpMethod POST               Matchers  lt HttpEntity lt List lt ObjectA gt  gt  gt any                Matchers  lt ParameterizedTypeReference lt List lt ObjectA gt  gt  gt any              thenReturn myEntity            List lt ObjectA gt  res   underTest getListofObjectsA            Assert assertEquals myobjectA  res get 0

[java] How do I mock a REST template exchange?

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