Different behavior between RestTestClient and WebTestClient

[lukas-krecan]

There is an inconsistency between WebTestClient and RestTestClient when the controller does not return any body. exec("/empty").returnResult().getResponseBody() in WebTestClient returns an empty byte[] while RestTestClient returns null.

See the reproducer here https://github.com/lukas-krecan/JsonUnit/compare/reproducer?expand=1

It's not a big deal, feel free to close it if it is intentional. I was just a bit surprised by that and thought you may not be aware.

[rstoyanchev]

There are some recent related changes in #35399, so worth using snapshots.

That said, I'm getting null with .exchange().expectBody().returnResult().getResponseBody() even with WebTestClient, which makes sense given the call to bodyToMono and block, which returns null if the Mono completes empty as a result of a response without any buffers.

I didn't try checking out the repository yet to see what's different.

[spring-projects-issues]

If you would like us to look at this issue, please provide the requested information. If the information is not provided within the next 7 days this issue will be closed.

[rstoyanchev]

I'm unable to reproduce the behavior, and I can't see how it would happen as explained in my last comment. I've now also tried to check out the project and run the tests, but I'm getting an error in IntelliJ:

java.lang.NoSuchMethodError: 'void org.apache.maven.cling.invoker.mvn.MavenInvoker.<init>(org.apache.maven.api.services.Lookup, java.util.function.Consumer)'

Please, provide a small isolated sample that demonstrates the behavior with WebTestClient returning an empty byte[].

[lukas-krecan]

Hi, the reproducer is here (The test fails)

[rstoyanchev]

Thanks, I was comparing WebTestClient (for WebFlux) vs RestTestClient it seems, but I see now that this is about WebTestClient for MockMvc, and there is a difference indeed.

In MockMvcWebTestClient,MockMvcHttpConnector gets the body from MockHttpServletResponse, which is an empty array, and that becomes the client response body.

In RestTestClient, MockMvcClientHttpRequestFactory does the same, but as requests are performed through RestClient, it has empty body checks that turn any empty body to null.

I would keep RestTestClient as it it is now since it's consistent with RestClient and WebTestClient (for WebFlux). It's MockMvcWebTestClient that's the odd one out, but that's superseded by RestTestClient and expected to eventually no longer be needed.

Thanks for the report. It was useful to consider, but closing with no further action planned.