Thursday, December 10, 2015

Visual Studio 2015 Update 1–Parallel Test Execution

If you are still looking for an excuse to start installing Visual Studio 2015 Update 1, here I got you one: a new feature that existed before but is now finally back in the box is Parallel Test Execution.

What is it?

From the release notes:

The Visual Studio Test Platform introduces support parallel execution of test cases.

Parallel test execution leverages the available cores on the machine, and is realized by launching the test execution engine on each available core as a distinct process, and handing it a container (assembly, DLL, or relevant artifact containing the tests to execute), worth of tests to execute. The unit of scheduling is the test container. Within each container, the tests will be executed as per the semantics of the test framework. If there are many such containers, then as processes finish executing the tests within a container, they are handed the next available container.

Parallel execution is supported through all launch points - CI, command line (CLI) and the IDE (Test Explorer, CodeLens, various “Run” commands, etc.), and the Test Explorer indicators track the progress of tests executing in parallel.

Getting started
  • Open Visual Studio 2015(don’t forget to install Update 1 first Glimlach)
  • Open the solution containing the tests.
    • Note that in order to leverage the Parallel Test Execution features, tests should be split out over multiple ‘containers’(assemblies)
  • Go to Test –> Test Settings –> Select Test Settings File
  • Select the .testsettings file you want to use.
    • If you don’t have a .testsettings file yet, just create an empty xml file and change the extension to .testsettings


  • Open the file in Visual Studio via File –> Open—> File… –> Open With(click on the small arrow next to the Open button) –> XML Editor
  • Paste the following code:
  • Change the MaxCPUCount value according to the following rules:
    • ‘n’ (where 1 <= n <= number of cores) : up to ‘n’ processes will be launched.
    • ‘n’ of any other value : The number of processes launched will be as many as the available cores on the machine.
  • Now run your tests…

Remark: I noticed that it only worked for MSTest. When using NUnit or XUnit no tests were executed.

1 comment:

pvlakshm said...

Thank you for the kind post. As I mentioned in the comment that I pointed to here:, this is supported for all test adapters; it should work for NUnit and tests as well. If you are not seeing that to be the case, it is a bug. Kindly send me a repro and I will get it investigated.