VSTS build failed test phase, but 0 tests failed

I had a strange situation where I have a build that suddenly starts signal failing tests, but actually zero test failed.

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Figure 1: No test failed, but the test phase was marked as failed

As you can see in Figure 1, the Test step is marked failed, but actually I have not a single test failed, indeed a strange situation. To troubleshoot this problem, you need to select the failing step to verify the exact output of the task.

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Figure 2: The output of the Test Step action is indeed test failed

As you can see in Figure 2, the VS component that executes the tests is reporting an error during execution, this imply that, even if no test is failing, something wrong happened during the test. This happens if any test adapter write to the console error during execution and it is done to signal that something went wrong.

Failing test run if there are error in output is a best practice, because you should understand what went wrong and fix it.

To troubleshoot the error you need to scroll all the output of the task, to find exactly what happened. Looking in the output I was able to find the reason why the test failed.

2017-11-17T14:43:19.6093568Z ##[error]Error: Machine Specifications Visual Studio Test Adapter – Error while executing specifications in assembly C:\A\_work\71\s\src\Intranet\Intranet.Tests\bin\Release\Machine.TestAdapter.dll – Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.

If an adapter cannot load an assembly, it will output error and the test run is marked as failed, because potentially all the tests inside that assembly were not run. This is a best practice, you do not want to have some test skipped due to load error and still have a green build.

Machine Specification test adapter tried to run test in Machine.TestAdapter.dll and this create a typeLoadException. Clearly we do not need to run test in that assembly, because TestAdapter.dll is the dll of the test adapter itself and does not contains any test. This problem indeed happens after I upgraded the nuget package of the runner, probably in the old version the TestAdapter.dll did not creates errors, but with the new version it does throw exception.

The problem lies in how the step is configured, because usually you ask to the test runner to run tests in all assemblies that contains Test in the name. The solution was to exclude that assembly from test run.

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Figure 3: How to exclude a specific dll from the test run

And voilà, the build is now green again. The rule is, whenever the test step is failing but no test failed, most of the time is some test adapter that was not able to run.

Gian Maria.

Multitargeting in DotNetCore and Linux and Mac builds

One of the most important features of DotNetStandard is the ability to run on Linux and Mac, but if you need to use a DotNetStandard compiled library in a project that uses full .NET framework, sometimes you can have little problems. Actually you can reference a dll compiled for DotNetCore from a project that uses full Framework, but in a couple of project we experienced some trouble with some assemblies.

Thanks to multitargeting you can simply instruct DotNet compiler to produce libraries compiled against different versions of frameworks, so you can simply tell the compiler that you want both DotNetStandard 2.0 and full framework 4.6.1, you just need to modify the project file to use TargetFrameworks tag to request compilation for different framework.

netstandard2.0;net461

Et voilà, now if you run dotnet build command you will find in the output folder both the versions of the assembly.

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Figure 1: Multiple version of the same library, compiled for different versions of the assembly.

Multitargeting allows you to produce libraries compiled for different version of the framework in a single build.

The nice aspect of MultiTargeting is that you can use dotnet pack command to request the creation of Nuget Packages: generated packages contain libraries for every version of the framework you choose.

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Figure 2: Package published in MyGet contains both version of the framework.

The only problem of this approach is when you try to compile multitargeted project in Linux on in Macintosh, because the compiler is unable to compile for the Full Framework. that can be installed only on Windows machines. To solve this problem you should remember that .csproj files of DotNetCore projects are really similar to standard MsBuild project files so you can use conditional options. This is how I defined multitargeting in a project

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Figure 3: Conditional multitargeting

The Condition attribute is used to instruct the compiler to consider that XML node only if the condition is true, and with Dollar syntax you can reference environment variables. The above example can be read in this way: if  DOTNETCORE_MULTITARGET environment variable is defined and equal to true, the compiler will generate netstandard2.0 and net461 libraries, otherwise (no variable defined or defined with false value) the compiler will generate only netstandard2.0 libraries.

Using the Condition attribute you can specify different target framework with an Environment Variable

All the people with Windows machines will define this variable to true and all projects that uses this syntax, automatically have the project compiled for both the framework. On the contrary, all the people that uses Linux or Macintosh can work perfectly with only netstandard2.0 version simply avoiding defining this variable.

The risk of this solution is: if you always work in Linux, you can potentially introduce code that compiles for netstandard2.0 and not for net461. Even if this situation cannot happen now, working with Linux or Mac actually does not compile and test the code against the full framework. The solution to this problem is simple, just create a build in VSTS that is executed on a Windows agent and remember to set DOTNETCORE_MULTITARGET to true, to be sure that the build will target all desired framework.

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Figure 4: Use Build variables to setup environment variables during the build

Thanks to VSTS / TFS build system it is super easy to define the DOTNETCORE_MULTITARGET at build level, and you can decide at each build if the value is true or false (and you are able to trigger a build that publish packages only for netstandard2.0). In this build I usually automatically publish NuGet package in MyGet feed, thanks to GitVersion numbering is automatic.

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Figure 5: Package published in pre-release.

This will publish a pre-release package at each commit, so I can test immediately. Everything is done automatically and is run in parallel with the build running in Linux, so I’m always 100% sure that the code compile both in Windows an Linux and tests are 100% green in each operating system.

Gian Maria.

Configure a VSTS Linux agent with docker in minutes

It is really simple to create a build agent for VSTS that runs in Linux and is capable of building and packaging your DotNetCore project, I’ve explained everything in a previous post, but I want to remind you that, with docker, the whole process is really simple.

Anyone knows that setting up a build machine often takes time. VSTS makes it super simple to install the Agent , just download a zip, call a script to configure the agent and the game is done. But this is only one side of the story. Once the agent is up, if you fire a build, it will fail if you did not install all the tools to compile your project (.NET Framework) and often you need to install the whole Visual Studio environment because you have specific dependencies. I have also code that needs MongoDB and Sql Server to run tests against those two databases, this will usually require more manual work to setup everything.

In this situation Docker is your lifesaver, because it allowed me to setup a build agent in linux in less than one minute.

Here are the steps: first of all unit tests use an Environment Variable to grab the connection string to Mongodb, MsSql and every external service they need. This is a key part, because each build agent can setup those environment variable to point to the right server. You can think that 99% of the time the connection are something like mongodb://localhost:27017/, because the build agent usually have mongodb installed locally to speedup the tests, but you cannot be sure so it is better to leave to each agent the ability to change those variables.

With this prerequisite, I installed a simple Ubuntu machine and then install Docker . Once Docker is up and running I just fire up three Docker environment, first one is the mongo database

sudo docker run -d -p 27017:27017 --restart unless-stopped --name mongommapv1 mongo

Than, thanks to Microsoft, I can run Sql Server in linux in a container, here is the second Docker container to run MSSQL

sudo docker run -e 'ACCEPT_EULA=Y' -e 'SA_PASSWORD=my_password' -p 1433:1433 --name msssql --restart=unless-stopped -d microsoft/mssql-server-linux

This will start a container with Microsoft Sql Server, listening on standard port 1433 and with sa user and password my_password. Finally I start the docker agent for VSTS

sudo docker run \
  -e VSTS_ACCOUNT=prxm \
  -e VSTS_TOKEN=xxx\
  -e TEST_MONGODB=mongodb://172.17.0.1 \
  -e TEST_MSSQL='Server=172.17.0.1;user id=sa;password=my_password' \
  -e VSTS_AGENT='schismatrix' \
  -e VSTS_POOL=linux \
  --restart unless-stopped \
  --name vsts-agent-prxm \
  -it microsoft/vsts-agent

Thanks to the –e option I can specify any environment variable I want, this allows me to specify TEST_MSSQL and TEST_MONGODB variables for the third docker container, the VSTS Agent. The ip of mongodb and MSSql are on a special interface called docker0, that is a virtual network interfaces shared by docker containers.

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Figure 1: configuration of docker0 interface on the host machine

Since I’ve configured the container to bridge mongo and SQL port on the same port of the host, I can access MongoDB and MSSQL directly using the docker0 interface ip address of the host. You can use docker inspect to know the exact ip of the docker container on this subnet but you can just use the ip of the host.

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Figure 2: Connecting to mongodb instance

With just three lines of code my agent is up and running and is capable of executing build that require external databases engine to verify the code.

This is the perfect technique to spinup a new build server in minutes (except the time needed for my network to download Docker images 🙂 ) with few lines of code and on a machine that has no UI (clearly you want to do a minimum linux installation to have only the thing you need).

Gian Maria.

Pause build and clear long build queue

In VSTS / TFS Build system, you can change the status of the build, between three states: Enabled, Paused and Disabled. The Paused state is really special, because all the build trigger are still active and builds are queued, but all these queued build does not starts.

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Figure 1: Paused build

Paused state should be used with great care, because if you forget a build in this state, you can end up with lots of queued build, as you can see in Figure 2:

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Figure 2: Really high number of build queued, because the build definition is paused.

What happened in Figure 2 is that some user probably set the build to paused, believing that no build will be queued, after some week he want to re-enabled, but we have 172 build in queue.

Now if you are in a situation like this, you probably need to remove all queued builds before re-enable the build definition. If you set the build to active you have the risk to completely saturate your build queue. To solve this problem, just go to the queued tab of the build page.

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Figure 3: Tab queued for the build page

From this page you can filter and show only queued build for the definition that was paused, you can then select all queued builds, and then delete all scheduling at once. Thanks to the filtering abilities present in the queued tab, you can quickly identify queued build and do massive operation on them.

Now that we deleted all the 172 queued build, we re-enabled the build without the risk of saturating build queue.

Gian Maria.

Dotnetcore, CI, Linux and VSTS

If you have a dotnetcore project, it is a good idea to setup continuous integration on a Linux machine. This will guarantee that the solution actually compiles correctly and all the tests run perfectly, even in  Linux environment. If you are 100% sure that, if a dotnetcore project runs fine under Windows it should run fine under Linux, you will have some interesting surprises. The first and trivial difference is that Linux filesystem is case sensitive.

If you use dotnetcore, it is  always a good idea to immediately setup a Build against a Linux environment to ensure portability.

I’m starting creating a dedicated pool for Linux machines. Actually having a dedicated pool is not necessary, because the build can require Linux capability, but I’d like to start having all the Linux build agent in a single place for easier management.

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Figure 1: Create a pool dedicated to build agents running Linux operating system

Pressing the button “download agent” you are prompted with a nice UI that explain in a really easy way how you should deploy your agent under your linux machine.

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Figure 2: You can easily download the agent from VSTS / TFS web interface

Instruction are detailed, and it is really easy to start your agent in this way: just running a configure shell script and then you can run the agent with another run.sh shell script.

There is also another interesting approach, you can give a shot to the official docker image that you can find here: https://github.com/Microsoft/vsts-agent-docker. The only thing I need to do is running the docker image with the command.

sudo docker run   -e VSTS_ACCOUNT=prxm -d -e VSTS_TOKEN=my_PAT_TOKEN-e VSTS_AGENT='schismatrix' -e VSTS_POOL='Linux' -it microsoft/vsts-agent

Please be patient on the first run because the download can take a little bit, the docker image is pretty big, so you need to patiently wait for the download to finish. Once the docker image is running, you should verify with sudo docker ps that the image is really running fine and you should check on the Agent Pool page if the agent is really connected. The drawback of this approach is that currently only Ubuntu is supported with Docker, but the situation will surely change in the future.

Docker is surely the most simple way to run a VSTS / TFS linux build agent.

Another things to pay attention is running the image with the –d option, because whenever you create a new instance of vsts agent from the docker base image, the image will download the latest agent and this imply that you need to wait a decent amount of time before the agent is up and running, especially if you, like me, are on a standard ADSL connection with max download speed of 5 Mbps.

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Figure 3: Without the –d option, the image will run interactively and you need to wait for the agent to be downloaded

As you can see from the image, running a new docker instance starts from the base docker image, contacts the VSTS server and download and install the latest version of the agent.

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Figure 4: After the agent is downloaded the image automatically configure and run the agent and you are up and running.

Only when the output of the docker image states Listening for Jobs the agent should be online and usable.

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Figure 5: Agent is alive and kicking

Another interesting behavior is that, when you press CTRL+C to stop the interactive container instance, the docker image remove the agent from the server, avoiding the risk to left orphan registration in your VSTS Server.

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Figure 6: When you stop docker image, the agent is de-registered to avoid orphan agents registration.

Please remember that, whenever you stop the container with CTRL+C, the container will stop, and when you will restart it, it will download again the VSTS agent.

This happens because, whenever the container stop and run again, it need to redownload everything that is not included in the state of the container itself. This is usually not a big problem, and I need to admit that this little nuance is overcome by the tremendous simplicity you have, just run a container and you have your agent up and running, with latest version of dotnetcore (2.0) and other goodness.

The real only drawback of this approach, is that you have little control on what is available on the image. As an example, if you need to have some special software installed in the build machine, probably you need to fork the container and configure the docker machine for your need.

Once everything is up and running (docker or manual run.sh) just fire a build and watch it to be executed in your linux machine.

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Figure 7: Build with tests executed in Linux machine.

Gian Maria