dotnet-test-slicer

Unit test slicer to support running NUnit tests on multiple test agents using 'dotnet test'.

A clever solution is provided in the AZDO docs for how to slice up the tests in a test assembly for an arbitrary number of test agents:

• Use dotnet test --list-tests to find all the tests
• Use a script to calculate which tests the agent should run, based on $(System.JobPositionInPhase) and $(System.TotalJobsInPhase)
• Pass those test names into dotnet test as a filter

Unfortunately there are issues with the provided approach:

• dotnet test --list-tests is not compatible with --filter so you have to run all tests in the test assembly which may not be desirable. (dotnet/sdk#8643)
• Passing test names (including test parameters) on the command line hits limitations with escaping certain characters and argument limits.

While the approach is good, we need a more robust solution for figuring out which tests each test agent should run.

This dotnet global tool:

• Uses the NUnit.Engine NuGet package to find all tests in a test assembly using the desired filter query.
• Slices the test list for the current test agent.
• Outputs the desired tests into an NUnit-specific .runsettings file that can be passed to dotnet test --settings foo.runsettings, bypassing command line arguments.

Usage

First install the global tool:

dotnet tool install -g dotnet-test-slicer

Run the slicer, providing the test assembly, an optional filter, and the slice parameters:

dotnet-test-slicer
  --test-assembly=MyUnitTests.dll
  --test-filter="cat != IgnoreTheseTests"
  --slice-number=1
  --total-slices=4
  --outfile=MyUnitTests.runsettings

Pass the .runsettings file to dotnet test to run the test slice:

dotnet test MyUnitTests.dll --settings MyUnitTests.runsettings