Kotlin Micronaut Mockk no answer found exception - kotlin

Question

I am new to the Micronaut framework and trying to test a demo example I created.
I am encountering the error io.mockk.MockKException: no answer found for: MathFacade(#3).computeAgain(3).
My code works as such - MathService invokes MathFacade. I want to test MathService so I mock MathFacade in my MathServiceTest with intentions to only test MathService.
My code is as below:
MathServiceTest
package io.micronaut.test.kotlintest
import io.kotlintest.specs.BehaviorSpec
import io.micronaut.test.annotation.MicronautTest
import io.micronaut.test.annotation.MockBean
import io.micronaut.test.extensions.kotlintest.MicronautKotlinTestExtension.getMock
import io.mockk.mockk
import io.mockk.every
import io.reactivex.Single
import kotlin.math.pow
import kotlin.math.roundToInt
#MicronautTest
class MathServiceTest(
private val mathService: MathService,
private val mathFacade: MathFacade
): BehaviorSpec({
given("the math service") {
`when`("the service is called with 3") {
val mock = getMock(mathFacade)
every { mock.computeAgain(any()) } answers {
Single.just(firstArg<Int>().toDouble().pow(3).roundToInt())
}
val result = mathService.compute(2)
then("the result is 9") {
mathService.compute(3).test().assertResult(27)
}
}
}
}) {
#MockBean(MathFacade::class)
fun mathFacade(): MathFacade {
return mockk()
}
}
MathService
package io.micronaut.test.kotlintest
import io.reactivex.Single
import javax.inject.Singleton
#Singleton
class MathService(private val mathFacade: MathFacade) {
fun compute(num: Int): Single<Int> {
return mathFacade.computeAgain(num)
}
}
MathFacade
package io.micronaut.test.kotlintest
import io.reactivex.Single
import javax.inject.Singleton
#Singleton
class MathFacade() {
fun computeAgain(num: Int): Single<Int>{
return Single.just(num*4)
}
}
Any help will be appreciated!