How to create an HttpResponse object with dummy values in ktor Kotlin? - kotlin

Question

I am using ktor for developing a microservice in Kotlin. For testing a method, I need to create a dummy HttpResponse (io.ktor.client.statement.HttpResponse to be specific) object with status = 200 and body = some json data.
Any idea how I can create it?

Answer 1

You can use mockk or a similar kind of library to mock an HttpResponse. Unfortunately, this is complicated because HttpRequest, HttpResponse, and HttpClient objects are tightly coupled with the HttpClientCall. Here is an example of how you can do that:
val call = mockk<HttpClientCall> {
every { client } returns mockk {}
coEvery { receive(io.ktor.util.reflect.typeInfo<String>()) } returns "body"
every { coroutineContext } returns EmptyCoroutineContext
every { attributes } returns Attributes()
every { request } returns object : HttpRequest {
override val call: HttpClientCall = this#mockk
override val attributes: Attributes = Attributes()
override val content: OutgoingContent = object : OutgoingContent.NoContent() {}
override val headers: Headers = Headers.Empty
override val method: HttpMethod = HttpMethod.Get
override val url: Url = Url("/")
}
every { response } returns object : HttpResponse() {
override val call: HttpClientCall = this#mockk
override val content: ByteReadChannel = ByteReadChannel("body")
override val coroutineContext: CoroutineContext = EmptyCoroutineContext
override val headers: Headers = Headers.Empty
override val requestTime: GMTDate = GMTDate.START
override val responseTime: GMTDate = GMTDate.START
override val status: HttpStatusCode = HttpStatusCode.OK
override val version: HttpProtocolVersion = HttpProtocolVersion.HTTP_1_1
}
}
val response = call.response

Answer 2

I did this with following. I only needed to pass a status code and description, so I didn't bother about other fields.
class CustomHttpResponse(
private val statusCode: Int,
private val description: String
) :
HttpResponse() {
#InternalAPI
override val content: ByteReadChannel
get() = ByteReadChannel("")
override val call: HttpClientCall
get() = HttpClientCall(HttpClient())
override val coroutineContext: CoroutineContext
get() = EmptyCoroutineContext
override val headers: Headers
get() = Headers.Empty
override val requestTime: GMTDate
get() = GMTDate()
override val responseTime: GMTDate
get() = GMTDate()
override val status: HttpStatusCode
get() = HttpStatusCode(statusCode, description)
override val version: HttpProtocolVersion
get() = HttpProtocolVersion(name = "HTTP", major = 1, minor = 1)}

Answer 3

With Ktor 2, it's best to use externalServices block instead of attempting to mock HttpResponse. That way you don't need to attempt and mock the internals of Ktor, and it's not complicated at all.
externalServices {
hosts("https://your-fake-host") {
routing {
get("/api/v1/something/{id}/") {
call.respondText(
"{}",
contentType = ContentType.Application.Json,
status = HttpStatusCode.OK
)
}
}
}
}
This need to be wrapped with testApplication