Spring Add an MockMVC alwaysDo equivalent to WebTestClient

In Spring Cloud Contract we're generating tests for our users. Typically what is being used is the RestAssured library for sending out HTTP requests. RestAssured has a MockMVC and WebTestClient extensions. The users can't modify the generated tests - what they can do is to write code in the base class that the generated test extends.

With MockMVC I could do the following

@ExtendWith(RestDocumentationExtension.class)
public abstract class BeerRestBase {
    ProducerController producerController = new ProducerController(oldEnough());
    StatsController statsController = new StatsController(statsService());

    private PersonCheckingService oldEnough() {
        return argument -> argument.age >= 20;
    }

    private StatsService statsService() {
        return name -> new Random().nextInt();
    }

    @BeforeEach
    public void setup(RestDocumentationContextProvider provider, TestInfo testInfo) {
        RestAssuredMockMvc.mockMvc(MockMvcBuilders.standaloneSetup(this.producerController, this.statsController)
                .apply(documentationConfiguration(provider))
                .alwaysDo(document(getClass().getSimpleName() + "_" + testInfo.getDisplayName()))
                .build());
    }
}

Notice the .alwaysDo(document(getClass().getSimpleName() + "_" + testInfo.getDisplayName())) part. We are running this assertion for each test method and each MockMVC call.

I'd like to achieve sth similar for WebTestClient.

I can write this:

WebTestClient webTestClient = WebTestClient.bindToController(this.producerController, this.statsController).configureClient()
                .filter(documentationConfiguration(provider))
                .build();
RestAssuredWebTestClient.webTestClient(webTestClient);

This is a fine way of hooking RestDocs to WebTestClient. I can't however make the global consumeWith(...) call like in the RestDocs snippet

this.webTestClient.get().uri("/").accept(MediaType.APPLICATION_JSON) 
        .exchange().expectStatus().isOk() 
        .expectBody().consumeWith(document("index")); 

It would be great to add sch a functionality.

cc @wilkinsona

Related issue:

https://github.com/spring-cloud-samples/spring-cloud-contract-samples/issues/106

Comment From: rstoyanchev

The challenge is that the body could be decoded in different ways, e.g. to a byte[], to some Object of type T or List<T>, or also to Flux<T> for external consumption via StepVerifier. We could provide a contract with hooks into all these ways and invoke the appropriate callback depending on what the test does. I'll experiment to see what comes out.