Introduce an alternative to WebTestClient based on RestClient

[EvaristeGalois11]

Hi, I searched the other issues discussing the introduction of RestClient but i couldn't find anything regarding this topic. I apologize if it's been already discussed somewhere.

Currently the only way to call a controller in a RANDOM_PORT environment is through TestRestTemplate (which is a spring boot addition) or with a RestClient instance built for the task. Both of this approaches aren't very nice, given that one must extract from the response object all the parts and then manually asserting on them. WebClientTest on the other hand has a really nice api with the assertions baked in, but it needs all the reactive stuff to be brought in.

A third party alternative is REST Assured which works quite well and has a very nice api, but it would be better i think to not have to rely on some external libraries for this type of thing.

Could it be possible to add a very similar api to WebTestClient (RestTestClient?) but without the reactive side of it?

[bclozel]

RestClient is using the same underlying infrastructure as RestTemplate. You can use the same testing infrastructure as a result.

Would spring-projects/spring-boot#37033 solve the problem for you?

[EvaristeGalois11]

But correct me if I'm wrong @bclozel, the problem is that the testing infrastructure for RestTemplate is very lacking because it was put in maintenance mode a long time ago.

This is how I'd call a controller with TestRestTemplate:

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
class SomeTestIT {
  @Autowired private TestRestTemplate rest;

  @Test
  void someTest() {
    var response = rest.getForEntity("/something", Something.class);
    assertThat(response.getStatusCode()).isEqualTo(HttpStatus.OK);
    assertThat(response.getBody()).usingRecursiveComparison().isEqualTo(expectedObject);
  }
}

There is basically nothing that helps testing the http call itself, all the assertions are manual.

This is instead how it's done with WebTestClient:

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
class SomeTestIT {
  @Autowired private WebTestClient webTestClient;

  @Test
  void someTest() {
    webTestClient
        .get()
        .uri("/something")
        .exchange()
        .expectStatus()
        .isOk()
        .expectBody(Something.class)
        .isEqualTo(expectedObject);
  }
}

It's just a much more polished and pleasant api to work with. Also it could easily be integrated with spring rest docs to generate some nice documentation, which couldn't be done with TestRestTemplate because it isn't supported 😢 .

Regarding spring-projects/spring-boot#37033 I don't think it is enough because they are discussing about a RestClient.Builder being provided by spring boot, which at most can permit to construct a bare bone RestClient which has the same problems of TestRestTemplate.