Cannot mock Retrofit call using MockWebServer

Question

I am trying to perform a unit test and mock a retrofit call using MockWebServer without success. When I run my test, it should run execute() block. When I test my code without CoroutineScope, it works. But I must launch that method in a coroutine scope.

How to successfully mock API call using MockWebServer inside CoroutineScope?

Test class:

private val mockWebServer = MockWebServer()

private val client = OkHttpClient.Builder()
    .build()

private val api = Retrofit.Builder()
    .baseUrl(mockWebServer.url("/"))
    .client(client)
    .addConverterFactory(GsonConverterFactory.create())
    .build()
    .create(SensorsApi::class.java)

@OptIn(DelicateCoroutinesApi::class)
private val mainThreadSurrogate = newSingleThreadContext("UI thread")

// ...

@OptIn(ExperimentalCoroutinesApi::class)
@BeforeAll
fun beforeAll() {
    Dispatchers.setMain(mainThreadSurrogate)
}

Test method:

@Test
fun `Loads sensors`() = runTest {
    val mDispatcher = object : Dispatcher() {
        override fun dispatch(request: RecordedRequest): MockResponse {
            val sensorsRegex = Regex("/")
            return if (request.path?.matches(sensorsRegex) == true) {
                MockResponse().setBody("[1]")
            } else {
                MockResponse().setResponseCode(500)
            }
        }
    }
    mockWebServer.dispatcher = mDispatcher

    //mockWebServer.enqueue(MockResponse().setBody("[1, 2, 3]"))

    viewModel.loadSensors()
}

Method I test in ViewModel:

fun loadSensors() {
    CoroutineScope(Dispatchers.IO).launch {
        sensorsService.getUserSensors("", "")
            .execute().let {
                println("inside getUserSensors()") // not executed
                if (it.isSuccessful) {
                    loadingDialog.postValue(Event(false))
                    consumeLoadedSensors(it)
                } else {
                    loadingDialog.postValue(Event(false))
                    showLoadSensorsFailure()
                }
            }
    }
}