The KTor docs state I can test my KTor module like...

# ktor

[Benoît Liessens]

The KTor docs state I can test my KTor module like this:

class ApplicationTest {
    @Test
    fun testRoot() = testApplication {
        application {
            module()
        }
        val response = client.get("/")
        assertEquals(HttpStatusCode.OK, response.status)
        assertEquals("Hello, world!", response.bodyAsText())
    }
}

Am I correct to state that above KTor app (module) isn’t started until the client GET request to “/” is performed?

Now the module I want to test does not have HTTP endpoints at all. The module start a set of background coroutines. In order to test the module I find myself doing an explicit call to startApplication() :

class ApplicationTest {
    @Test
    fun testRoot() = testApplication {
        environment {
           // load particular config
        }
        application {
            myModuleWithCoroutines()
        }
        
        startApplication()
        // assert outcome of coroutines
    }
}

Above works, but I have no means to stop the KTor module. There is no stopApplication() counterpart which prevents me to have a 2nd test (method) with different configuration. What is the advised approach here to start and stop my non-HTTP KTor module?
Thanks

[Aleksei Tirman [JB]]

Am I correct to state that above KTor app (module) isn’t started until the client GET request to “/” is performed?

That's correct.

What is the advised approach here to start and stop my non-HTTP KTor module?

Unfortunately, the stop method of the TestApplication class cannot be called by the users due to visibility restrictions. The only way I found is to get the application property via reflection:

// ...
startApplication()
// assert outcome of coroutines

val appProp = ApplicationTestBuilder::class.memberProperties.first { it.name == "application" }
val app = appProp.get(this) as TestApplication?
app?.stop()

[Lidonis Calhau]

I am probably missing something.
Why do you need Ktor if you do not have HTTP endpoints ?

[Benoît Liessens]

We do have a few http endpoints but not in this module though. We picked ktor because we wanted coroutines and a lightweight app framework (not sping boot).

[Benoît Liessens]

Some feedback to close the thread…. eventually there was no need to explicitly stop KTor after the tests, testApplication {} did does that just fine.
What I was missing in my KTor module, was proper logic to close (cancel) the coroutines. Adding this was enough:

monitor.subscrbe(ApplicationStopping) {
  // cancel whatever coroutines was launched by the KTor module. 
}

Additionally, also the supervisorScope{} created in my KTor module had to be cancelled.