Category: Uncategorized (Page 1 of 14)

TLDR; Make sure all your async methods return a type of Task<something> and not just Task or Void! this will cause sporadic crashes of your application. Only use asyn void or async Task on event handlers.

Longer version:

Recently I worked on an app build in Xamarin and found myself in a nasty situation. My app would crash in the debugger and leave no trace what was going on. In the device Log I could find the following message:

Time Device Name Type PID Tag Message
04-08 18:22:28.908 nexus_api_27 Error 4058 DEBUG Abort message: ‘* Assertion at /Users/builder/jenkins/workspace/xamarin-android-d16-0/xamarin-android/external/mono/mono/mini/debugger-agent.c:4407, condition is_ok (error)' not met, function:set_set_notification_for_wait_completion_flag, <strong>Could not execute the method because the containing type 'System.Runtime.CompilerServices.AsyncTaskMethodBuilder1[System.Collections.Generic.IEnumerable`1[T_REF]]’, is not fully instantiated. assembly: type: member:(null)

The nasty part was that when you step through the code in the debugger the application would just crash under your fingers and you could not step through the code that was causing this. And this message is useless as well since it does not show where things go wrong. Only stepping through the debugger revealed a part of the code where the debugger would exit without any message and the app crashed as well.

You can see at various placed more developers experience this issue. e.g.:

https://github.com/xamarin/xamarin-macios/issues/4380

The code that was causing the crash looked as follows:

The issue lies in the method calls that have await, but don’t expect a result.

The signatures of the methods InitializeStore(), PullLatestAsync() and AnnotateFavorites() all returned a Task, but not a Task<T>. This results in the fact that the method call is more or less fire and forget method and you don’t really have to wait for the result to be returned.

It is important that you change the method signatures to e.g. return a Task<bool> where the boolean is only signaling success or failure of the method call.

I was able to rewrite those methods to all return a boolean value and this resolved the issue of the method exiting without any results.

You can find more on best practices of using async and await here: https://msdn.microsoft.com/en-us/magazine/jj991977.aspx

Hope this helps you resolve this issue as well.

Recently Microsoft added the capability to CodedUI to test on the Edge browser. For this they extended the cross browser playback capability. This uses Selenium under the hood. So the steps to make this work are as follows:

• Install the plugin “Selenium components for Coded UI Cross Browser Testing” from the Visual Studio Gallery (found here)
• Download the Edge driver that matches your windows 10 version (found here)
• Install the driver to the following location : %ProgramFiles(x86)%\Microsoft Web Driver

And finally in the code you need to switch the browser you want to launch. You need to provide the following name to start edge:”MicrosoftEdge”

BrowserWindow.CurrentBrowser = “MicrosoftEdge”; 

And that is it!

Happy testing on Edge

If you attended one of my sessions, I hope you enjoyed them. I had a great time.

For your reference you can find the PDF’s here and the accompanying demo code.

Continuous delivery on azure: A/B testing, Canary releasing and Dark launching

If you are more interested in Continuous delivery, you also might like my just published course at Pluralsight called “Building a Continuous Delivery Pipeline with TFS and Visual Studio 2015” which you can find here: https://www.pluralsight.com/courses/tfs-visual-studio-2015-implementing-continuous-delivery

My second session was on Micro Services and you can find the PDF here:

VSH11 Exploring Microservices in a Microsoft Landscape

And the final session was on building maintainable cross browser UI tests with either selenium or codedUI. The PDF can be found here:

VSH16 Writing Maintainable X-Browser Automated Tests

and you can find the demo’s here: Search google

Also if you want to learn more about CodedUI, you can also watch one of my two courses I build for Pluralsight here:Test Automation with CodedUI Pluralsight which explains in detail all that can be done with CodedUI and Testing Web Applications with CodedUI Pluralsight which is focused on testing web applications.

if you don’t have a subscription yet, you can watch it for free with the free trial

Hope you enjoyed it, if you have comments or feedback let me know!

Cheers,

Marcel

In my previous post about Deploying ASP.NET 4.5 to Docker on Windows I forgot to mention that you might run into an issue when running webdeploy.

Julian Perrott, commented on my post and asked if this is an issue. I think it is an issue and that the install does not complete correctly. But there is an easy fix for this as well. What you can do is add a small PowerShell script to your Docker image and run that after the first attempt to deploy the website. Then the next step is to run the script to fix the ACL’s and then again run web deploy. I have not yet tried this on the latest Windows server 2016 bits, but on the Technical preview 5 this worked like a charm.

You need the following script to fix the ACL’s:

This script doe nothing more then getting the ACL on the path and then re-apply it. this will make windows fix the ACL and make them in canonical form again.

You can add this to your dockerfile and make it part of your standard install of a website in your release pipeline.

So this does nothing more then adding the little PowerShell script to the container and then using that in the step after deploying your website

Hope this helps!

I was just doing my work on windows 10 and for no apparent reason the windows 10 start menu would not respond anymore to either my Windows hotkey on the keyboard or by clicking on the start menu icon in the left bottom corner. This meant no response to the windows key and me typing the application I wanted to start, not being able to shut down my machine, etc. So this gave me some real headaches because the only way I could solve this is do a reset of my PC or just repaving my machine and install windows 10 again.

This has happen to me several times and most of the time after I had been doing some Mobile App development where I build mobile apps that are cross platform. Lately I had to do this for my talk at VS Live in Las Vegas and for that I had to turn on developer mode on my windows 10 machine.

Now I am not sure if his issue is caused by the mobile development I have done or if it is just my SSD drive acting up on me and corrupting certain files on my system. I do know that running the following powers shell command (started in administrator mode of course) solved the problem form me:

The option DisableDevelopmentMode does the following:

Registers an existing app package (.appx) installation that has been disabled, didn’t register, or has become corrupted. Use DisableDevelopmentMode to specify that the manifest is from an existing installation and not from a collection of files in development mode.

At least this was a way to solve it for me and hopefully it will work for you as well.

I have been playing around with this idea for quite some time and I already build this for a customer in the past, but after questions I got from people using CodedUI who tried to come up with a simplified syntax I thought it would be time to publish what I have at the moment.

If you hand code your test automation with CodedUI, then you know that searching for a control is always a couple of lines of code to set up a search. You first create an instance of the control you need, provide it the search scope in the constructor and next you need to set the search properties. Once that is done you can then use the control and the moment you use one of it’s properties it will search for your control.

With Selenium this is a bit different. You have the Driver class that provides more or less to primary methods. FindElement and FindElements and you provide it an instance of the By class that contains the search criteria.

Let me illustrate what I mean with two examples. Bot do the same. We goto the google home page and type a search query.

CodedUI:

Selenium:

In general I hear that people like the Selenium syntax more then the multistep aproach in codedUI. The thing I dislike is that I lose the type safety of the type of control. So the question is, would it be possible to get the same syntax for codedUI and still use codedUI and get a type safe way of interacting with the search controls?

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Recently I joined a project where they are working on a new application that is based on the new ASP.NET cross platform tooling. While this is still in beta at the moment I write this, we strongly believe in the future of ASP.NET and the ability to run it on multiple platforms. Of course we want this project to start with everything done right from the start, so we are not only writing clean code, we also embrace the continuous delivery concepts and with that we have a strong need of continuous integration and continuous tests. This means we are writing Unit tests from day one and want those integrated in our build system. For the build we use Team Foundation Server 2015 and the new cross platform build system. The challenge I want to discuss today is that the tooling at the moment is still a lot in flux so the unit test tooling for testing cross platform solutions is not fully up to par as you are used to in the “classic” ASP.NET world on just windows.

So when we want to write unit tests, we need to ensure we use a test framework that also supports running on multiple platforms. At the moment XUnit is the test tooling that is already available for DNX. So let me describe the steps involved for making a set of unit tests and run those tests on the new build platform in TFS 2015.

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