[FIXED] Mock all methods except one in JUnit test with Mockk llibrary

Issue

How to mock or spy some methods but use real logic of another method in the same class using Mockk library?

Here is a simplified logic of parent-child classes that I have:

open class Parent() {
    var condition = true
    fun method1() {
        if (condition) {
            method2("bum")
        } else {
            method3(41)
        }
    }

    fun method2(someStr: String): String {
        //some complicated logic
        return "some result"
    }

    fun method3(someInt: Int): Int {
        //some complicated logic
        return 42
    }
}

class Child: Parent() { }

And a test that I want to have:

 @Test
 fun `when condition is true, it should call method2`() {
    clearAllMocks()

    val child: Child = mockk()
    child.condition = true
    every { child.method2(any()) } returns "something"
    every { child.method3(any()) } returns 11

    child.method1()

    verify(exactly = 1) { child.method2(any()) }
}

Of course this logic for testing doesn't work. But how I can call real method1 but mock method2 and method3?

Solution

The way to mock some methods with Mockk except one:

    @Test
    fun `when condition is true, it should call method2`() {
        clearAllMocks()

        val child: Child = spyk()
        every { child.condition } returns true
        every { child.method2(any()) } returns "something"
        every { child.method3(any()) } returns 11
        //every { child.method1() } answers { callOriginal() } - this works with and without this line

        child.method1()

        verify(exactly = 1) { child.method2(any()) }
    }

It's possible to do with spyk and it's obligatory to mock a behavior of methods that need to be mocked with every. For non-mocked method add nothing or to be sure that its behavior is unambiguous - you can add callOriginal

Answered By - Alexey Simchenko
Answer Checked By - David Goodson (JavaFixing Volunteer)