Partial mocking and unnecessary stubbings feature conflict #1345

ghilainm · 2025-02-05T13:24:02Z

When activating CheckUnnecessaryStub and using partial mocking feature, an unnecessary stubb is wrongly detected when a mock which is a property of the object partially mocked. Below is a minimal example to reproduce the issue.

Non working example (multiplier as a property):

import io.mockk.every
import io.mockk.junit5.MockKExtension
import io.mockk.mockk
import org.junit.jupiter.api.extension.ExtendWith
import kotlin.test.Test
import kotlin.test.assertEquals

data class Multiplier(
    val value: Int,
)

// Class to be tested
class Calculator(
    val multiplier: Multiplier,
) {
    // Call original
    fun multiply(a: Int): Int = a * multiplier.value
}

@ExtendWith(MockKExtension::class)
@MockKExtension.CheckUnnecessaryStub
class CalculatorTest {
    @Test
    fun `test partial mocking and unnecessary stubbing`() {
        val calculator = mockk<Calculator>()
        // Partial mock
        every { calculator.multiply(2) } answers { callOriginal() }

        val multiplier = mockk<Multiplier>()
        every { calculator.multiplier } returns multiplier
        every { multiplier.value } returns 10

        assertEquals(20, calculator.multiply(2))
    }
}

Code above raises the following error:

Unnecessary stubbings detected.
Following stubbings are not used, either because there are unnecessary or because tested code doesn't call them :

Calculator(#1).getMultiplier())
java.lang.AssertionError: Unnecessary stubbings detected.
Following stubbings are not used, either because there are unnecessary or because tested code doesn't call them :

Calculator(#1).getMultiplier())
at io.mockk.impl.recording.CommonVerificationAcknowledger.checkUnnecessaryStubHelper(CommonVerificationAcknowledger.kt:79)
at io.mockk.impl.recording.CommonVerificationAcknowledger.checkUnnecessaryStub(CommonVerificationAcknowledger.kt:30)
at io.mockk.MockKDsl.internalCheckUnnecessaryStub(API.kt:287)
at io.mockk.MockKKt.checkUnnecessaryStub(MockK.kt:400)
at io.mockk.junit5.MockKExtension.afterAll(MockKExtension.kt:95)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1597)

Working Example (multiplier as function)

import io.mockk.every
import io.mockk.junit5.MockKExtension
import io.mockk.mockk
import org.junit.jupiter.api.extension.ExtendWith
import kotlin.test.Test
import kotlin.test.assertEquals

data class Multiplier(
    val value: Int,
)

// Class to be tested
class Calculator {
    fun multiplier() = Multiplier(5)

    // Call original
    fun multiply(a: Int): Int = a * multiplier().value
}

@ExtendWith(MockKExtension::class)
@MockKExtension.CheckUnnecessaryStub
class CalculatorTest {
    @Test
    fun `test partial mocking and unnecessary stubbing`() {
        val calculator = mockk<Calculator>()
        // Partial mock
        every { calculator.multiply(2) } answers { callOriginal() }

        val multiplier = mockk<Multiplier>()
        every { calculator.multiplier() } returns multiplier
        every { multiplier.value } returns 10

        assertEquals(20, calculator.multiply(2))
    }
}

The text was updated successfully, but these errors were encountered:

VitalyVPinchuk · 2025-04-23T14:04:35Z

Hi
I think it comes down to this:

class CTest {
    class C {
        open val a = 1
        val b = 1 // the issue, b is final
        fun c() = 1
        fun op() = a + b + c()
    }

    @Test
    fun `track final value`() {
        val mock = mockk<C>()
        every { mock.a } returns 2
        every { mock.b } returns 2
        every { mock.c() } answers { 2 }
        every { mock.op() } answers { callOriginal() }

        assertEquals(6, mock.op()) // ok
        verify { mock.a }
        verify { mock.b } // fails
        verify { mock.c() }
    }
}

@Raibaz Is there a way to track final val?

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Partial mocking and unnecessary stubbings feature conflict #1345

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