I'm trying to write unit tests for a post request but I'm having problems with the serialization:

Fail to serialize body. Content has type: class .models.NewWord, but OutgoingContent expected.
java.lang.IllegalStateException: Fail to serialize body. Content has type: class .models.NewWord, but OutgoingContent expected.
If you expect serialized body, please check that you have installed the corresponding plugin(like `ContentNegotiation`) and set `Content-Type` header.

My test according to the docs (2.0.0 btw) :

testApplication {
                val c = createClient {
                    install(ContentNegotiation) {
                        json()
                    }
                }
                val r = c.post("/word") {
                    contentType(ContentType.Application.Json)
                    setBody(NewWord("a", "b", "c"))
                }
            }

I also tried header() instead of contentType() but doesn't work either

header(HttpHeaders.ContentType, ContentType.Application.Json.toString())

the NewWord class is Serializable ofc. what am I missing?

Can you check that you import

ContentNegotiation

from

io.ktor.client.plugins

?

io.ktor.client.plugins.*

I mean, I have this import

my guess was that there are two

ContentNegotiation

plugins, for server and for client. It’s possible that you use one for server. The code will still compile, because there is

install

in the scope of

testApplication

too

yeah you're right

We may need to add

@DslMarker

to these builders. Thanks for your report

Here is another issue.