Is there any way to mimic the configuration of an

HttpClient

using a different engine? Let's say I have the following in my production code:

val DEFAULT_CLIENT = HttpClient() {
    install(JsonFeature) {
        serializer = KotlinxSerializer(kotlinx.serialization.json.Json {
            ignoreUnknownKeys = true
        })
    }
}

and then in my testing code I have the following:

val client = HttpClient(MockEngine) {
    engine {
        addHandler { request ->
            respond(...)
        }
    }
    install(JsonFeature) {
        serializer = KotlinxSerializer(kotlinx.serialization.json.Json {
            ignoreUnknownKeys = true
        })
    }
}

As you can see, the client configuration must be the same, so I can reproduce the client behaviour in the tests, and then I configure the

MockEngine

to respond whatever I want... I have found the following: •

HttpClient

has a constructor which takes an

engine

and a

userConfig

, but ◦

userConfig

is declared as

private val

and I can't find any public getter ◦ I don't know if I can create a shareable

HttpClientConfig

, as ▪︎ I don't explicitly use an engine in the production code, as this is a multiplatform project (iOS / Android) and I let Ktor to select the default engine per platform ▪︎

HttpClientConfig

has a type parameter

HttpClientEngineConfig

which seems to depend on the engine • You have a config method, which lets you build a new

HttpClient

with additional configuration, but you can't switch to a different engine using this So the only way I can think of to be able to do this is try to declare a shared

HttpClientConfig<*>.() -> Unit

fun

which then I can use in both instantiations. Anyway this seems like a common use case with a bit convoluted solution. Is there any other simpler way to do what I want to do?

I usually do something like

class ApiClient(engine: HttpClientEngine) {
    private val httpClient = HttpClient(engine) {
        // shared client config
    }
}

Then in prod I pass the relevant platform engine like

ApiClient(Ios.create()

or

ApiClient(Android.create()

and in tests

ApiClient(MockEngine { ... })

ok, I see, you can use a pre-configured

MockEngine

... I didn't know you could do that, thanks!

I like passing the platform engine explicitly because it lets you do engine-specific config if needed. But if you don't need that then what you have should work fine.

Well, this way you have both, you can just omit the engine, and you'll have the default one, or you can pass one (either a

MockEngine

or a real one) and configure it as you want