Junit 4 在 kotlin 中测试内部类

Question

I use Junit4 and kotlin.

I use the Enclosed for the inner class test.

import org.junit.Test
import org.junit.experimental.runners.Enclosed
import org.junit.runner.RunWith

@RunWith(Enclosed::class)
class SampleTest {

    var text = "parent class"

    class Class1 {
        @Test
        fun `print the text`() {
            println(text)
        }
    }

    inner class Class2 {
        @Test
        fun `print the text`() {
            println(text)
        }
    }

}

in Class1 and Class2, need the text variable.

I use the inner for an access child class to parent class.

but I have a problem, the test function is removed and I can't test that. see the photo.

can I test the inner class in kaolin with Junit4?

Answer 1

Class1 is a plain nested class that happens to be in SampleTest . It's just an organisational thing, your Class1 instance doesn't have any reference to a SampleTest instance, so it can't access text (not without being passed an instance explicitly).

If you want a nested class to be able to access an enclosing instance like that, you need to mark it as inner , like with Class2 . That way you can create an instance of Class2 through an instance of SampleClass , like

val sample = SampleClass()
val class2 = sample.Class2()
sample.text = "wow!"
class2.`print the text`()

You can read about this stuff in the docs if it's unfamiliar

So yeah, if JUnit constructs a Class1 instance, it doesn't know what text is, since that's an instance variable in some other unrelated class.

And I'm assuming it doesn't know how to create Class2 , since it requires a SampleTest instance to do that. All the examples for Enclosed use static nested classes, and likethe Java docs say :

A static nested class interacts with the instance members of its outer class (and other classes) just like any other top-level class. In effect, a static nested class is behaviorally a top-level class that has been nested in another top-level class for packaging convenience.

so that's basically the same as Kotlin's (non-inner) nested classes, like your Class1 . You probably can't use inner classes (not to organise and automatically run tests, anyway)

You probably want to stick text in a companion object if you're organising your tests in classes (or just a top-level object outside of SampleClass , or just in the top level of the file if you really want - just somewhere it can be accessed by any other class in a "static" way

Answer 2

we can use 3 wayes

1. use NestedRunner this

2. use HierarchicalContextRunner this

3. use Enclosed and the companion object and don't use the inner class

   @RunWith(Enclosed::class)

   class TEST {

    companion object { var text = "parent class" } class Class1 { @Test fun `print the text`() { println(text) } } class Class2 { @Test fun `print the text`() { println(text) } }

   }