Parameterized Test in Kotlin usign mehtod source for nested test class

Question

I may use case the class under test has many cases so it is divided into a structure of inner classes. I want to write parameterized test cases to reduce boiler plate and code duplication. For this I wanted to go with the approach of method source. Class under test

class UnderTest
{
    testThisMethod(a:String,b:String?){
        // Do something
        externalInterface.call(a?:b) 
    }
}

Test Case structure

internal class A() {
    private val externalService = mockk<ExternalService>
    private val test: UnderTest(externalService)

    // Some general tests
    //---Position Outter
    inner class A {
        //--- Position A
        inner class B {
            //--- Position C
            @ParameterizedTest
            @MethodSource("provideArguments")
            fun `with arguments external service create object`(
                argument1: String,
                argument2: String,
                expected: String
            ) {
                // Some code
                verify {
                    externalService.call(expected)
                    //some more verification
                }
            }
        }
    }
}

To provide the argument provider method I tried placing it at positions and got following errors

• Position outer: initialization error :Could not find factory method in class
• Position A,B: compilation error: companion not allowed here

How can this be achieved?

Answer 1

Try using @TestInstance(TestInstance.Lifecycle.PER_CLASS)

internal class A() { private val externalService = mockk private val test: UnderTest(externalService)

// Some general tests
//---Position Outter
inner class A {
    //--- Position A
    @TestInstance(TestInstance.Lifecycle.PER_CLASS)
    inner class B {
        //--- Position C
        @ParameterizedTest
        @MethodSource("provideArguments")
        fun `with arguments external service create object`(
            argument1: String,
            argument2: String,
            expected: String
        ) {
            // Some code
            verify {
                externalService.call(expected)
                //some more verification
            }
        }
    }
}

}

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