create a pipeline azure devops code coverage report

To have there published report you need to use Cobertura. For TRX you will get only link to download file. And to create Cobertura report you need to install in your test projects coverlet.collector nuget package. Here you have code which should fix your problem:

# You just added coverlet.collector to use 'XPlat Code Coverage'
- task: [email protected]
  displayName: Test
  inputs:
    command: test
    projects: '**/*Tests/*.csproj'
    arguments: '--configuration $(buildConfiguration) --collect:"XPlat Code Coverage" -- RunConfiguration.DisableAppDomain=true'
    workingDirectory: $(Build.SourcesDirectory)

- task: [email protected]
  inputs:
    command: custom
    custom: tool
    arguments: install --tool-path . dotnet-reportgenerator-globaltool
  displayName: Install ReportGenerator tool

- script: ./reportgenerator -reports:$(Agent.TempDirectory)/**/coverage.cobertura.xml -targetdir:$(Build.SourcesDirectory)/coverlet/reports -reporttypes:"Cobertura"
  displayName: Create reports

- task: [email protected]
  displayName: 'Publish code coverage'
  inputs:
    codeCoverageTool: Cobertura
    summaryFileLocation: $(Build.SourcesDirectory)/coverlet/reports/Cobertura.xml  

[2021 UPDATE]

You don’t need extra tasks to install/run the custom ReportGenerator tool: it is now the default tool for reading coverage.cobertura.xml files and is included in the dotnet CLI.

By default, it will save the cobertura xml file to the temp directory on the agent, though. So, you just need to update the summaryFileLocation of the PublishCodeCoverageResults task to point to the temp directory and skip the “middle man” steps:

# You just added coverlet.collector to use 'XPlat Code Coverage'
- task: [email protected]
  displayName: Test
  inputs:
    command: test
    projects: '**/*Tests/*.csproj'
    arguments: '--configuration $(buildConfiguration) --collect:"XPlat Code Coverage"'

- task: [email protected]
  displayName: 'Publish code coverage'
  inputs:
    codeCoverageTool: Cobertura
    summaryFileLocation: '$(Agent.TempDirectory)/**/coverage.cobertura.xml'

If you have multiple test projects which generates multiple coverage files please use these steps after test commad. It will merge files before publishing them:

  - task: [email protected]
    displayName: "Merge code coverage reports"
    inputs:
      reports: "**/coverage.cobertura.xml"
      targetdir: "$(Build.ArtifactStagingDirectory)/coverlet"
      reporttypes: "Cobertura"
      verbosity: "Verbose"

  - task: [email protected]
    displayName: "Publish code coverage results"
    inputs:
      codeCoverageTool: Cobertura
      summaryFileLocation: "$(Build.ArtifactStagingDirectory)/coverlet/Cobertura.xml"