.Net

Faking HTTP Context for your unit tests

Posted on by trailmax

While writing and testing ASP.Net MVC application, many times over I needed to simulate HTTP Request and presence of HttpContext.Current. I need this mostly when I try to test code that interacts with MVC framework, like MVC Action Filters or custom Model Binders or testing routes.

ASP.Net MVC 4 is quite good in this matter – most of the framework can be replaced by a mocked object and there is a minimum number of static calls or sealed objects. So you can do the HTTP Simulation, but usually it involves a lot of boiler-plate code and many mock-objects to be set-up.

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How to test code for accessing Azure Storage REST Api

Posted on by trailmax

Update: There is an updated implementation of this code: see this blog post

One of my applications has a feature where it is given a URL with Shared Access Signature to Azure Blob Storage and then via REST API it uploads files to the storage. You can do that by provided Azure Storage libraries. Originally I had that functionality implemented with these libraries. But now I’m slimming down the application (this is a small command line app) and getting rid of unnecessary dependencies. And for the sake of one upload method I don’t want to tie myself to masses of extra DLLs. So I’m replacing the libraries with REST API call.

I have spent some time trying to test this functionality. You may say that this is a not a unit test. Yes, it is not a unit test. Other questions? Also you may say that you shouldn’t test these kind of things and wrap a class around these and ignore. That is what I have done in the past, but that particular piece of code caused an endless pain because I’ve done it all wrong and it was not covered by tests.

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Error handling in MVC and nice error pages

Posted on by trailmax

It is vital for your application security not to show any internals when error happen. And you should be able to replace all internal error messages to nice user-friendly pages. It is a just nice for users – they are not getting splashes of oil, when engine is exploded, also another measure to improve site security.

There are lot of articles about error handling in ASP.Net MVC, but most of them do not cover the whole range. There is a very good resource on this, and I do recommend reading and understanding that first.

With error handling there are a lot of edge cases, and for every single one of them you need to provide a solution, otherwise your error messages will talk too loud about your implementation and that can lead to security vulnerability.

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Elmah Shinangiens. Part 2.

Posted on by trailmax

In my last post I talked about ELMAH and how you can override connection string. But Atif Aziz (ELMAH author) pointed out that there is a better way to do that:


Fair enough, I thought. I did see that solution when originally needed to fix this problem. But I did not manage to quickly reproduce the code, so I went with a hacky way. This time I’ve spent a couple hours for that and did get what I wanted without dirty hacks.

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ELMAH in Azure and Connection Strings business

Posted on by trailmax

ELMAH is a nifty tool that allows to you record exceptions that arise in your web-application. It is very handy and everyone should use it in addition to application logging. But if you are using Dependency Injection and have your connection strings provided by some service, then you might have trouble. For example, in our app, we use Azure Configuration settings and we have a service IConfiguration that has a lot of get-methods for different config settings in our app, including database connection string.

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Test your constructors to be simple

Posted on by trailmax

In the previous blog post I wrote how it is important to have a simple constructor that only accepts dependencies. And violation of this rule cost me at least 12 hours of debugging and blocking issue for some developers in the team. Now I have a unit test to prevent this kind of problem in the future.

One of the suggestions in the comments was to use strict mocks and inject them into a controller. And don’t set up any kind of expectations on mocks. This way if dependencies are doing anything in the controller, they will fail the test.

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Constructors should be simple

Posted on by trailmax

Whole day of yesterday I’ve spent debugging some “random” error that came up third time during this week. The issue did go away after some tribal dances around the code, but two other instances did not get resolved easier. The biggest problem was that only one of the developers on the team did get the issue, and everybody else were not affected. And the same happened in the new deployment. And the issue was quite major – the whole site did not load. Nothing beyond the login screen. And it was impossible to hook in the debugger, it was bypassing all the breakpoints.

I would’ve gone through the issue and try debugging it, by my machine was not affected by the problem. I could not reproduce the issue locally. But on my home machine the issue came up. Strange I through, but was glad it came up – means I can dig my teeth deep in the problem and debug it.

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Upload files to Azure Blob Storage with using Shared Access Keys

Posted on by trailmax

I had a task of uploading files from command line client to a private container in Azure Blob Storage. And as part of the overall infrastructure I also has MVC4 and WebApi sites running on my Azure Web-Site installation.

The problem with uploading files was that the container was private. Before, every time I used the container, I used private key to access it, but all the operations were contained on the server: user submits a file in a form in a browser, file is passed through MVC web-site, where it is uploaded into Azure blob storage. And in MVC there is a very easy way to manage multiple uploaded files.

Now my task was similar, but as a client I had command line application and server side was WebApi. In WebApi it is not so easy to manage uploaded files, especially if you had multiple files for upload. You could not (or I could not find a way to do that) simply redirect the upload stream from controller into Azure Blob. You had to store file somewhere and then copy that to Azure storage. And there are a few problems with that:

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Ignore test categories in TFS build server using DefaultTemplate.xaml

Posted on by trailmax

At the moment I’m using excellent service from Microsoft: hosted TFS. The service is still in the preview (15 July 2013) and some features are in beta, but it works pretty smoothly already. One of the things I had to learn is how to use TFS as a build server. I’ve used to nice TeamCity with almost drag-and-drop build steps and simple configuration management. TFS is using XAML definition file to drive the build process. The default template that comes with any project is pretty much covers everything you might need when you start, but it is very complex and when you try looking on the XAML diagram, you might want to run away – it’s that big and complex. That’s what I did first time I looked on the XAML processes. Run away and installed TeamCity.

Now I’ve decided to give it another go. I’ve started from enabling nUnit tests on build server. By default TFS only works with MSTest. To enable nUnit, you need to add nUnit assemblies and nUnit to MSTest adapter to your source control. The process is perfectly described in this post by Ajay Majgaonkar. I’ve also seen the description of the process in some Microsoft documentation, but have lost the link.

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Quartz.Net in Azure with Autofac. Smoothness.

Posted on by trailmax

Quartz.Net is an awesome scheduler for .Net world. It is a copy-cat from Java brother. The documentation is pretty useless, as it has not been updated for a while. The docs are useful to understand the general principals of operation, but examples of code usually don’t work. Instead the download provided on the site has a lot of examples. Use them as a guidance. Read the code, documentation sucks.

Anyway, I’ve spent couple days trying to get Quartz.Net to work inside of Azure and with Autofac dependency injection. And there are a few lessons that I’ve learned that I would like to share.

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