Hi folks, I'm writing some tests and I need a way to post operations to the main queue and make th...

# kotlin-native

[Omar Mainegra]

Hi folks, I'm writing some tests and I need a way to post operations to the main queue and make the test case wait for the queue to be empty before finishing (What I tried to do the the sleep without success)

@Test
fun `This test doesn't execute the println statement`() {
    dispatch_async(dispatch_get_main_queue()) {
        println("dispatch_async")
    }

    NSThread.sleepForTimeInterval(1.0)
}

I'm thinking about something similar to XCTestExpectation. Any thoughts?

[Kris Wong]

are your tests running on the main thread (sounds like yes)?

[Omar Mainegra]

Yes, println("$isMainThread") prints true

[Kris Wong]

so obviously if you block the test you are blocking the main thread

[Kris Wong]

you need to use the run loop

[Omar Mainegra]

That's right, but the run loop doesn't work either

dispatch_main()

throws

Uncaught Kotlin exception: kotlin.native.IncorrectDereferenceException: illegal attempt to access non-shared common.platform.ConcurrencyModelTests.$This test doesn't execute the println statement$lambda-8$FUNCTION_REFERENCE$726@8b6ede08 from other thread

[Kris Wong]

yes, you need to freeze anything that you're passing to another thread

[Omar Mainegra]

Sorry, but I'm not passing anything

@Test
fun `This test doesn't execute the println statement`() {
    Platform.isMemoryLeakCheckerActive = false

    dispatch_async(dispatch_get_main_queue()) {
        println("dispatch_async")
    }

    dispatch_main()
}

[Kris Wong]

sure you are, you're passing the block

[Omar Mainegra]

Sure I was

@Test
fun `This test doesn't execute the println statement`() {
    Platform.isMemoryLeakCheckerActive = false

    val block = {
        println("dispatch_async")
    }
    
    dispatch_async(dispatch_get_main_queue(), block.freeze())

    dispatch_main()
}

[Omar Mainegra]

Now I need a way to stop the loop

[Kris Wong]

you can just process the loop until it's empty

[Kris Wong]

i don't recall whether GCD uses the run loop or not

[Omar Mainegra]

Looks like CFRunLoopRun and CFRunLoopStop could work

[Kris Wong]

NSRunLoop would give you a more convenient API

[Omar Mainegra]

Sweet, this works

@Test
fun `This test does execute the println statement`() {
    dispatch_async(dispatch_get_main_queue(), {
        println("dispatch_async")
    }.freeze())

    NSRunLoop.currentRunLoop.runUntilDate(NSDate.dateWithTimeInterval(1.0, NSDate.now))
}

[Omar Mainegra]

Thanks a lot

[Kris Wong]

nice