Hi, I'm trying to write unit tests for a websocket client and I was looking at the tests on ktor. :t...

# ktor

[Osman Saral]

Hi, I'm trying to write unit tests for a websocket client and I was looking at the tests on ktor. 🧵

[Osman Saral]

This test passes, But when I change "null" to "foo" it doesn't fail with assertion, instead it throws kotlinx.coroutines.channels.ClosedReceiveChannelException: Channel was closed. Is there something wrong or is it normal.

@Test
    fun testJsonNullWithWebsocketsClient(): Unit = testApplication {
        install(io.ktor.server.websocket.WebSockets)
        routing {
            webSocket("/") {
                for (frame in incoming) {
                    assertEquals("null", (frame as Frame.Text).readText())
                    outgoing.send(frame)
                }
            }
        }

        createClient {
            install(WebSockets) {
                contentConverter = KotlinxWebsocketSerializationConverter(
                    Json {
                        ignoreUnknownKeys = true
                    }
                )
            }
        }.ws("/") {
            val user: User? = null
            sendSerialized(user)
            val received = receiveDeserialized<User?>()
            assertNull(received)
        }
    }

[Aleksei Tirman [JB]]

I cannot reproduce the ClosedReceiveChannelException . Can you please share a complete test where that exception is thrown during the execution?

[Osman Saral]

https://github.com/osrl/ClosedReceiveChannelException
you can reproduce using this repo

[Aleksei Tirman [JB]]

The problem is that the assertEquals("error", (frame as Frame.Text).readText()) fails but the assertion exception doesn’t propagates to the top level. Then the test server Websockets connection is closed which leads to closing the receive channel on the client side.

[Osman Saral]

This shouldn't happen right? We should see the exception.

[Aleksei Tirman [JB]]

You can see it by wrapping a handler with try/catch .

[Osman Saral]

Is it possible to close the connection manually? Just signal server to close or vise versa?

[Osman Saral]

What causes to close the connection?

[Aleksei Tirman [JB]]

Also, I can see the ComparisonFailure in the logs.

[Aleksei Tirman [JB]]

The assertion error causes closing of a connection

[Aleksei Tirman [JB]]

On the client side you can call the close method to close a connection.

[Osman Saral]

but i can't read close frames from serverside. right?

[Aleksei Tirman [JB]]

They are handled automatically if the connection isn’t raw.

[Osman Saral]

how do you run the tests? I can't see the ComparisonFailure in the logs. Or any other exception other than ClosedReceiveChannelException, That makes things very hard

[Osman Saral]

I'm running them using the IDE

[Aleksei Tirman [JB]]

I have logs configured for JVM. I’m unsure how to do this for Android.

[Osman Saral]

This is actually a kmm project. But still the same. Do you know any documentation about logging, or any lead you can show me?

[Osman Saral]

adding org.slf4j:slf4j-simple to the project did the trick