Configure WebTestClient for @AutoConfigureMockMvc tests

[bclozel]

Spring Framework recently added WebTestClient support for testing Spring MVC applications using MockMvc (see spring-projects/spring-framework#19647).

Right now, Spring Boot offers two ways to test a web application: using TestRestTemplate on a running web server or with MockMvc (no actual server involved).

We should consider MockMvcTestClient and how we should update our testing infrastructure and documentation with this new option.

[Sam-Kruglov]

I can see there is already a MockMvcWebClientAutoConfiguration, why not create a similar MockMvcWebTestClientAutoConfiguration?
Here's how I'm doing it and it seems to work fine:

@BeforeEach
void setUp(@Autowired MockMvc mockMvc) {
    webTestClient = MockMvcWebTestClient.bindTo(mockMvc).build();
}

1 note: ParameterNamesModule missing from the default Jackson2JsonDecoder. Could use ObjectMapper#findAndRegisterModules

[nightswimmings]

@philwebb Does this mean we can use @AutoConfigureMockRestServiceServer with WebTestClient as well, so internal WebClient/RestTemplate calls can be mocked from the test? If so we could update documentation and also okhttp would not be needed anymore as explained here right? spring-projects/spring-framework#19852

[bclozel]

MockRestServiceServer is not related to MockMvc and it only binds to RestTemplate.

Even if it did, we would be missing important parts of the WebClient features (like streaming). So the current advice still stands.

[nightswimmings]

Ok, thanks! I thought that the fact WebTestClient supported now MockMVC enabled somehow the use of MockRestServiceServer for internal mocking