Mocking Spring’s reactive WebClient in Kotlin, using MockK for UnitTests

This is purely a quick Note To Self, so that I can find it again, when googling for it 🤓

Let’s assume we want to test a method, invoking a WebClient call in a Unit Test (no Integration Test). Example:

private fun loadSomething(id: String): SomeThing {
    return runBlocking(Dispatchers.IO) {
        webClient
            .get()
            .uri("/someurl/{id}", id)
            .exchangeToMono { response ->
                if (response.statusCode() == HttpStatus.OK) {…