Cannot install ContentNegotiation in the testApplication

Question

I am following the documentation to unit test a ktor API. In particular configuring the HttpClient for ContentNegociation with conversion of a class to JSON (https://ktor.io/docs/testing.html#configure-client)

Note the application starts and the POST endpoint works.

Here is the test code:

class DeviceInformationRouteTest {

    @Test
    fun testPostDeviceInformation() = testApplication {
        val client = createClient {
            install(ContentNegotiation) { // Error on the `install` call
                json()
            }
        }
        val deviceInformation = DeviceInformation("test")

        val response = client.post("/deviceInformation") {
            setBody(deviceInformation)
        }
        assertEquals("""{"value": "test"}""",response.bodyAsText())
        assertEquals(HttpStatusCode.OK, response.status)
    }
}

The problem is that the compilation fails saying:

DeviceInformationRouteTest.kt: (19, 13): 'fun <P : Pipeline<*, ApplicationCall>, B : Any, F : Any> install(plugin: Plugin<ApplicationCallPipeline, ContentNegotiationConfig, PluginInstance>, configure: ContentNegotiationConfig.() -> Unit = ...): Unit' can't be called in this context by implicit receiver. Use the explicit one if necessary

If needed, my partial build.gradle:

plugins {
    application
    kotlin("jvm") version "1.7.10"
    id("io.ktor.plugin") version "2.1.1"
    id("org.jetbrains.kotlin.plugin.serialization") version "1.7.10"
}

dependencies {
    implementation("io.ktor:ktor-server-content-negotiation-jvm:2.1.1")
    implementation("io.ktor:ktor-server-core-jvm:2.1.1")
    implementation("io.ktor:ktor-serialization-kotlinx-json-jvm:2.1.1")
    implementation("io.ktor:ktor-server-netty-jvm:2.1.1")
    testImplementation("io.ktor:ktor-server-tests-jvm:2.1.1")
    testImplementation("org.jetbrains.kotlin:kotlin-test-junit:1.7.10")
}

I believe this is exactly as in the example, I don't know why it is failing to compile.

Answer 1

So it turned out I needed a different ContentNegociation plugin, from the client package. In the build.gradle.kts:

dependencies {
    // ...
    testImplementation("io.ktor:ktor-client-content-negotiation:2.1.1")
}

and in the test, use the correct import:

import io.ktor.client.plugins.contentnegotiation.*

// ...
    @Test
    fun testPostDeviceInformation() = testApplication {
        val httpClient = createClient {
            install(ContentNegotiation) {
                json()
            }
        }
    // ...
    }
// ...