I’m struggling a little with testing JSON in a pos...

# ktor

[Jonathan Hollingsworth]

I’m struggling a little with testing JSON in a post request.
It fails within the Ktor tests, but if I send a direct HTTP request in via curl or whatever, it works fine. Totally stumped - any help would be much appreciated.

[Jonathan Hollingsworth]

My test is pretty light-weight at the moment

withTestApplication({ configureRouting() }) {
            with(handleRequest(<http://HttpMethod.Post|HttpMethod.Post>, "/preview", ) {
                addHeader(HttpHeaders.ContentType, ContentType.Application.Json.toString())
                setBody(Json.encodeToString(Entity(name="test", description="A test description")))
            }) {
                assertEquals(HttpStatusCode.OK, response.status())
            }
        }

And the Route definition even more so

post("/preview") {
            val config = call.receive<Entity>()
            call.respondText(call.receiveText())
        }

It fails Cannot transform this request's content to <package>.Entity

[Jonathan Hollingsworth]

Interestingly, if I swap out call.receive<Entity>() with Json.decodeFromString<Entity>(call.receiveText()) it seems to work. I’d have thought they were functionally similar.

[Landry Norris]

I've had issues with the JSON feature before. I usually just switch it out to Json.decodeFromString and wait. Usually it's because of a problem in my code, and call.receive works once I fix it. It's much easier to debug this way.

[Aleksei Tirman [JB]]

Could you please share the code for a complete test cause the following code works as expected?

import io.ktor.application.*
import io.ktor.features.*
import io.ktor.http.*
import io.ktor.request.*
import io.ktor.response.*
import io.ktor.routing.*
import io.ktor.serialization.*
import io.ktor.server.testing.*
import kotlinx.serialization.ExperimentalSerializationApi
import kotlinx.serialization.Serializable
import kotlinx.serialization.encodeToString
import kotlinx.serialization.json.Json
import org.junit.Test
import kotlin.test.assertEquals

class SomeTest {
    @OptIn(ExperimentalSerializationApi::class)
    @Test
    fun test(): Unit = withTestApplication({ configureRouting() }) {
        application.install(ContentNegotiation) {
            json()
        }

        with(handleRequest(<http://HttpMethod.Post|HttpMethod.Post>, "/preview", ) {
            addHeader(HttpHeaders.ContentType, ContentType.Application.Json.toString())
            setBody(Json.encodeToString(Entity(name="test", description="A test description")))
        }) {
            assertEquals(HttpStatusCode.OK, response.status())
            assertEquals("A test description", response.content)
        }
    }
}

fun Application.configureRouting() {
    routing {
        post("/preview") {
            val config = call.receive<Entity>()
            call.respondText(config.description)
        }
    }
}


@Serializable
data class Entity(val name: String, val description: String)

[Jonathan Hollingsworth]

Thank you so much, that code works great.
I hadn’t installed the ContentNegotiation in the test.