I’m trying to run my test suite which uses koin multithreaded and it does not work as expected. I ju...

# koin

[christophsturm]

I’m trying to run my test suite which uses koin multithreaded and it does not work as expected. I just want multiple koin instances to be independent from each other.
this test illustrates the problem:

@Test
    fun `multi instance koin`() {
        class User()

        val user = User()

        val myModule = module {
            single {user}
        }
        fun app()  = koinApplication { modules(myModule) }
        val koin1 = app()
        val koin2 = app()

        koin1.koin.get<User>()
        koin1.close()
        koin2.koin.get<User>()


    }

[christophsturm]

after closing koin1, koin2 no longer works

[tynn]

What’s the issue there?

[christophsturm]

The last statement fails

[christophsturm]

And it’s unclear to me why.

[tynn]

Well, if it fails, you get information about why it fails. And that’s the key to it. Which exception do you get?

[christophsturm]

Did you try to understand what this test does?

[christophsturm]

it works when i change it to this:

@Test
fun `multi instance koin`() {
    fun module() = module { single { User() } }

    fun app() = koinApplication { modules(module()) }
    val koin1 = app()
    val koin2 = app()

    koin1.koin.get<User>()
    koin1.close()
    koin2.koin.get<User>()
}

[christophsturm]

so I think koinApplication should just copy the modules to make one application self contained.

[christophsturm]

I would have expected that modules are immutablw

[tynn]

Now I do. And you’re right. Modules are mutable and contain their loaded state.

[christophsturm]

i think thats really suprising and not how an api should behave. why is it that way?

[tynn]

@arnaud.giuliani maybe you could explain?

[christophsturm]

let me also explain why its suprising to me: I use a tdd approach and I also always run the tests in parallel. the parallel test running not only makes the tests faster, but it also shows if i rely on global state. (which is bad)

[arnaud.giuliani]

Koin can’t be fully isolated, as by default we are using a static context

[arnaud.giuliani]

the module declaration is filled to a variable, then not a Lazy thing

[arnaud.giuliani]

I don’t understand the case within the example here

[christophsturm]

its just a simplified example to show that when i close one koin server the other server that uses the same module definitions no longer works

[christophsturm]

its a mimized test case for a problem i saw when trying to run integration tests in parallel.

[christophsturm]

when i change it to always create a new copy of the module definition (by making it a function instead of a val) like the second snippet, it works

[christophsturm]

and I think its really suprising that the first example fails

[arnaud.giuliani]

because finally you use the same module reference

[arnaud.giuliani]

🤔