Sherlock configuration - Build server integration

Monday, January 13, 2014 | Posted in Jenkins MsBuild Sherlock TeamCity

Once the configuration of Sherlock is complete the last step needed to make use of automatic regression testing is to integrate with a build server. In this post I will explain which steps need to be taken to integrate Sherlock with a build server. Examples will be given for Jenkins, which is used at my work, and TeamCity, which I use personally.

In order to integrate with a build server you will need to:

  • Create at least one test configuration
  • Write the build scripts necessary to register a test, wait for the completion of the test and process the results.
  • Set up a job on the build server to execute the test.

Test configurations

In order to execute a test the first thing you need to decide on is the test configuration which will be executed. In Sherlock the test configuration is described by a XML file similar to the following gist:

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In this configuration file replace all instances of ${SOME_TEXT}$ with the appropriate information. Note that some configuration settings should be templated so that those values can be supplied by the build system, e.g. the application version number:

  • Provide an application name and version for use in the test report.
  • Provide a compact description. This will be used as the title of the test report
  • Provide each environment with a name. It doesn't matter what that name is as long as it is consistently used throughout the configuration file. All test steps which should be executed on the same environment should be linked to the same environment name. Note that while it is possible to request multiple environments to be started in a test, it is not possible to synchronize those environments. In other words each environment will exit as soon as it completes the test steps assigned to it, no environment will wait for other environments to complete their work.
  • For each test step that needs to be executed provide the order (integer number starting at 0, incrementing for each step), the name of the environment in which the step should be executed, the failure mode, either Stop or Continue and the correct file paths. Note that the test steps use the following definitions for their file paths:
    • msi: file is the absolute path to the MSI file as on the machine that is used to register the test (i.e. the origin).
    • x-copy: destination is the absolute path to the directory that will hold all the x-copy results on the test environment.
    • x-copy: base is the absolute path to the directory that holds the files / directories to be x-copied on the origin.
    • x-copy: paths contains the absolute paths to the files / directories that should be x-copied. It is expected that these all reside in the base directory at some level.
    • script: file is the absolute path to the script file on the origin.
    • console: exe is the absolute path to the executable that should be executed on the test environment. Note that the path is also pointed to the test environment. Hence the CONSOLE test step is the only test step that doesn't copy files.
    • All test steps: All files and directories that should be included in the report are absolute paths on the test environment.
    • notification: The absolute path where the final report should be placed. This path should be accessible to both Sherlock (the master controller) and the application that will process the test results.
  • It makes sense to always copy back any logs that are written during the test. If you don't need them for test failure diagnosis then it is easy to delete them later, however you can't copy them from the test environment after the test has completed because the test environment will be reset to its original state upon shut down.

If you need tests to run in different environments or with different test steps then you will need to create a configuration file for each environment / set of test steps.

Build scripts

The easiest way to execute the test from a build server is to create a set of build scripts that can do the work for you. In this example I will be using MsBuild as the scripting language.

In order to create the configuration file from the template it is necessary to replace all the templated configuration settings with their current values. The following gist shows an inline MsBuild task that does exactly that:

In order to use this task create an ItemGroup with the identifiers of the settings and their replacement values. For example:

If this example is used on the following template file:

Then the outcome is the following output file:

The next step will be to create a build script that can register the test with the Sherlock system. This can either be done with a call to the exec task or with the following inline MsBuild task:

The next step is a little tricky in that it is now necessary to wait for Sherlock to execute the test and create the test report. The tricky bit due to the fact that Sherlock will only execute the tests when a suitable test environment is available. That means that tests could be executed almost immediately if an environment is directly available, or not for a long time if all environments are busy. On top of that MsBuild does not have the ability to watch specific files. The following inline task allows you to wait for certain files to be created. Note that you need to provide a time-out which determines how long this task will wait for the report files. How long this time-out should be depends on:

  • How long it takes for the tests to execute.
  • How many tests will be executed on the same test environments. Tests executing on different test environments can be run in parallel provided the hardware will stand up to it.
  • How many other tests may potentially be executing at the same time.

Finally the report files need to be checked for success or failure. For each test Sherlock produces a HTML and an XML report. The easiest way to find the outcome of a test is to parse the XML report and search for the result element. The value of this element will either be Passed or Failed. The following inline task will accomplish this goal:

Build jobs

The final task is to setup one or more build jobs for the build server to execute. While you can combine the testing steps with the build steps it is in general advisable to have a separate job for the testing steps. The main reason for that is that the the testing steps can take quite a while to execute, ranging from several minutes to hours, which slows down the continuous integration feedback cycle considerably. Based on the idea that the tests should be contained in their own build job the following set-up is proposed.

  • Define three different build jobs for the build, test and deploy stages of the process. This means that each job will be responsible for a specific task. Individual jobs will be use the artefacts produced by the other jobs.
  • Set up dependencies between the different builds where required. For instance the test job will depend on the artefacts produced by the build job.
  • The build job can be run both as continuous integration build, i.e. execute the build job each time a commit to the source control system is detected, and as pre-requisite to the test job.
  • Similarly the test job could be run nightly to provide relatively quick feedback on regression problems while also acting as pre-requisite to the deploy job.
  • If the version number includes either the build counter of the build job or the revision number of the source control commit then special care needs to be taken for the test and deploy jobs in order to ensure that they get the same numbers as the build job did.
  • In a similar fashion it will be necessary to control the version control settings so that all builds pull in the same revision. One solution would be to store the revision index in the first job in the chain and then transfer that to the other jobs.

For the two build systems I have specifically worked with the following additional notes can be made:

  • Jenkins
    • In addition to the three standard jobs you will probably need a Build flow job to trigger the different standard jobs in the right order. This has to be done because at the moment it does not seem possible in Jenkins to trigger pre-requisite builds without having the downstream project taking up one of the build executors. The build flow jobs live outside the actual build executors which makes it possible to optimize the use of the executors.
    • In order to deal with the build number problems as specified above the simplest way is to write the number to a file in the upstream job, archive that and then pull it out in the downstream jobs. The same goes for the version control information.
  • TeamCity
    • Downstream jobs have both a snapshot dependency and an artefact dependency on the upstream job. The snapshot dependency takes care of the synchronization of the version control revision. Note that you should create different VCS roots for each project, otherwise the projects all share a single check-out directory. By sharing a single directory it is possible that upon starting the second job the directory is cleaned which will likely remove the artefacts from the first job.
    • The build number can be copied easily by synchronizing the build numbers.
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