GitLab CI流水线中dotnet-reportgenerator无法找到coverage.cobertura.xml，如何避免重复构建解决该问题？

Let's break down your issue and fix it without repeating the build step.

The Problem #

You're trying to reuse the build artifacts from your build stage in the unit-tests stage with --no-build, but the coverage.cobertura.xml files aren't being found by reportgenerator. When you remove --no-build, it works but runs an unnecessary second build.

Why This Happens #

When you use --output build with dotnet test --no-build, the test results (including coverage files) get generated in the build directory structure instead of the test project's default TestResults folder. Your original reportgenerator command was searching for **/coverage.cobertura.xml across the entire repo, but the files were actually tucked away in the build directory (or not being generated correctly because of misaligned output paths with the pre-built artifacts).

Fixes to Avoid Redundant Builds #

Here are a couple of reliable solutions to get this working while reusing your build artifacts:

Solution 1: Explicitly Set the Test Results Directory #

Specify where test results (and coverage files) should be saved, then point reportgenerator to that exact location:

unit-tests:
  stage: unit-tests
  script:
    - |-
      # Generate coverage files in a predictable subdirectory of build
      dotnet test --no-build --output build --results-directory build/TestResults --collect:"XPlat Code Coverage"
      # Install reportgenerator tool
      dotnet tool install -g dotnet-reportgenerator-globaltool
      # Target the specific path where coverage files were saved
      reportgenerator -reports:'build/TestResults/**/coverage.cobertura.xml' -targetdir:'CoverageReports' -reporttypes:'Cobertura'
  artifacts:
    reports:
      cobertura: CoverageReports/Cobertura.xml
  dependencies:
    - build

Solution 2: Use Coverlet Directly for More Control #

Instead of relying on the XPlat Code Coverage collector, use Coverlet's MSBuild properties to generate coverage files directly to a fixed path. This avoids the random GUID-named folders and makes file lookup straightforward:

unit-tests:
  stage: unit-tests
  script:
    - |-
      # Generate coverage files directly to a Coverage folder
      dotnet test --no-build --output build -p:CollectCoverage=true -p:CoverletOutput=./Coverage/ -p:CoverletOutputFormat=cobertura
      # Install reportgenerator tool
      dotnet tool install -g dotnet-reportgenerator-globaltool
      # Pick up the coverage files from the fixed path
      reportgenerator -reports:'Coverage/**/*.cobertura.xml' -targetdir:'CoverageReports' -reporttypes:'Cobertura'
  artifacts:
    reports:
      cobertura: CoverageReports/Cobertura.xml
  dependencies:
    - build

How These Work #

• Solution 1 uses --results-directory to force all test output (including coverage files) into a predictable location under your pre-built build directory. This lets reportgenerator easily find the files without searching the entire repo.
• Solution 2 leverages Coverlet's native MSBuild parameters to generate coverage files directly to a specified folder, skipping the default random subfolders entirely. This is often more reliable for CI/CD pipelines where consistent paths are key.

Both approaches let you keep the --no-build flag, so you're reusing the build artifacts from the build stage and eliminating the redundant build step.

内容的提问来源于stack exchange，提问作者user13755987