Spring Expose MvcResult in WebTestClient

It would be great to access the MvcResult in the WebTestClient validation flow.

Currently, if you want to validate eg. the exception message and type, you have to:

webTestClient.post()
        ...
    .expectBody()
    .consumeWith(rsp -> {
             MvcResult mvc = ((MvcResult) rsp.getMockServerResult());
             assertEquals("expected message", mvc.getResolvedException().getMessage());
             assertTrue(mvc.getResolvedException() instanceof MyCustomException);
         });

It would be great if that could just be integrated and asserted inside the builder flow, if possible?

Comment From: bclozel

I think you're looking for MockMvcWebTestClient#resultActionsFor:

FluxExchangeResult<Person> result = webTestClient.post().uri("/people/123")
                .exchange().returnResult(Person.class);

MockMvcWebTestClient.resultActionsFor(result).andExpect(mvcResult -> 
                assertThat(mvcResult.getResolvedException()).hasMessageContaining("expected message").isInstanceOf(MyCustomException.class));

Does this work?

Comment From: membersound

While this might work, it would still be better if you could write mvcResult assertions directly in the WebTestClient builder method flow, like .exchange().expect(mvcResult -> assertThat(mvcResult.getResolvedException()).hasMessageContaining("expected message").isInstanceOf(MyCustomException.class));

Comment From: bclozel

MockMvcWebTestClient transitively imports spring-webmvc classes, whereas WebTestClient has been designed initially for WebFlux usage. Implementing your suggestion would make Spring MVC a requirement here. This is not a change we want to introduce.

I'm closing this issue as a result.

Comment From: membersound

Then the migration docs are a bit mislead, as they pretend that WebTestClient is a direct replacement for MockMvc: https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.6-Release-Notes#using-webtestclient-for-testing-spring-mvc

This change also enables WebTestClient for Spring MVC in mock environments: classes annotated with @AutoConfigureMockMvc can get injected a WebTestClient. This makes our support complete, you can now use a single API to drive all your web tests!

And I think being able to test with a single API, as suggested, would be indeed the best way.

Comment From: bclozel

WebTestClient is focusing mainly on HTTP messages. To me, this sentence means that you can use the same client for mock and live server integration tests. MockMvcWebTestClient provides a lot of additional features, but MockMvc is definitely not deprecated, so keeping it in your test suite is perfectly fine.

Comment From: membersound

I can confirm that .resultActionsFor() is sufficient to support some validation actions on MockMvc that are not possible inside the WebTestClient builder flow.