With ktor 2.3.12, we have some tests that use `Tes...

# ktor

[xenomachina]

With ktor 2.3.12, we have some tests that use TestApplicationCall instances. They do something like this to create them:

val environment = createTestEnvironment { }
val application = Application(environment)
val call = TestApplicationCall(
    application = application,
    coroutineContext = coroutineContext
)
call.request.addHeader("X-Zaphod-Heads", "2")

// test code that uses the `ApplicationCall` goes here

After upgrading to 3.0.0, this code no longer works. We can't create an Application using Application(environment), and TestApplicationCall needs an Application.

The tests themselves actually just need ApplicationCall instances. The only thing TestApplicationCall has that we use that isn't also in ApplicationCall is request.addHeader (ie: TestApplicationReqest.addHeader on the request property.)

What's the right way to do this with ktor 3.0.0?

[Aleksei Tirman [JB]]

The right way is to rewrite the tests to use the testApplication method or the ApplicationTestBuilder (https://ktor.io/docs/server-testing.html). Here is an example:

@Test
fun test() = runTest {
    val builder = ApplicationTestBuilder().apply {
        application {
            routing {
                get("/") {
                    call.response.header("custom", "value")
                    call.respond(HttpStatusCode.OK)
                }
            }
        }
    }

    val response = builder.client.get("/")
    assertEquals(response.headers["custom"], "value")
}

[xenomachina]

This particular test isn't trying to send requests to an application and then make assertions about the response.

[xenomachina]

We have a function that we use in `CallLoggingConfig.format`:

fun callLogFormatter(
    call: ApplicationCall,
    clock: () -> Long
): String {
    ...
}

...

install(CallLogging) {
    ...
    val clock = ::getTimeMillis
    clock(clock)
    format { call -> callLogFormatter(call, clock) }

[xenomachina]

We have some tests of callLogFormatter that:
1. create an ApplicationCall with various request properties (method, headers, path, etc.), response properties (eg: status code) and attributes (eg: CallStartTime)
2. pass the call to callLogFormatter
3. assert that the result of callLogFormatter is what we expect
With ktor 2.x we just directly created a TestApplicationCall, which made it fairly easy to construct an ApplicationCall we could pass to callLogFormatter without having to go through routing or other complications.

How can we do that with ktor 3.0.0?

[Aleksei Tirman [JB]]

Unfortunately, the testApplication API doesn't allow creating a separate ApplicationCall object. You can use the following code to test the callLogFormatter :

@Test
fun test() = testApplication {
    routing {
        get {
            call.response.header("custom", "value")
            callLogFormatter(call) {
                123
            }

            // Make assertion
        }
    }

    client.get("/")
}

[Aleksei Tirman [JB]]

I've created an issue to address this limitation.

[Osip Fatkullin]

Here is a workaround you could try to use to get an instance of Application :

@Test
fun test() = testApplication {
    lateinit var application: Application
    application { application = this }
    startApplication()
    
    val call = TestApplicationCall(
        application = application,
        coroutineContext = coroutineContext
    )
}

[xenomachina]

Thank you both!

@Aleksei Tirman [JB], is there a way to capture all requests in the testApplication? That is, instead of:

get { /* response setup and assertions */ }

is there an alternative to get that routes all HTTP methods?