Spring WebFlux, unit testing Mono and Flux

gervais.b :

Interested in reactive programming, I played a bit with the Building a Reactive RESTful Web Service guide. And wanted to move forwrad and add some unit tests.

I tried to test my handler (RouterFunction) with plain Junit/Mockito test. But, because it is reactive, the handler returns a Mono<ServerResponse>. So I had to block() it to test the ServerResponse status but was not able to extract his body to test it. While searching the web for a solution, it seems that all the samples are using the WebTestClient.

My question is:

Given that all samples are using WebTestClient to test a reactive REST service and that it is not easier to (unit) test the body of a ServerResponse. Is it a good practice to unit test a RouterFunction or is it better to always do broader tests with the WebTestClient ?

Thanks a lot.

gervais.b :

It seems that the best practice is to use the WebTestClient. However this one can be used without a running server;

The spring-test module includes a WebTestClient that can be used to test WebFlux server endpoints with or without a running server.

-- https://docs.spring.io/spring/docs/5.0.0.BUILD-SNAPSHOT/spring-framework-reference/html/web-reactive.html#web-reactive-tests