79 lines
3.2 KiB
Markdown
79 lines
3.2 KiB
Markdown
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---
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type: reference, howto
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---
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# Test Coverage Visualization
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> [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/3708) in GitLab 12.9.
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With the help of [GitLab CI/CD](../../../ci/README.md), you can collect the test
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coverage information of your favorite testing or coverage-analysis tool, and visualize
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this information inside the file diff view of your merge requests (MRs). This will allow you
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to see which lines are covered by tests, and which lines still require coverage, before the
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MR is merged.
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## How test coverage visualization works
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Collecting the coverage information is done via GitLab CI/CD's
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[artifacts reports feature](../../../ci/yaml/README.md#artifactsreports).
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You can specify one or more coverage reports to collect, including wildcard paths.
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GitLab will then take the coverage information in all the files and combine it
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together.
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For the coverage analysis to work, you have to provide a properly formated
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[Cobertura XML](https://cobertura.github.io/cobertura/) report to
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[`artifacts:reports:cobertura`](../../../ci/yaml/README.md#artifactsreportscobertura).
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This format was originally developed for Java, but most coverage analysis frameworks
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for other languages have plugins to add support for it, like:
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- [simplecov-cobertura](https://rubygems.org/gems/simplecov-cobertura) (Ruby)
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- [gocover-cobertura](https://github.com/t-yuki/gocover-cobertura) (Golang)
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Other coverage analysis frameworks support the format out of the box, for example:
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- [Istanbul](https://istanbul.js.org/docs/advanced/alternative-reporters/#cobertura) (JavaScript)
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- [Coverage.py](https://coverage.readthedocs.io/en/coverage-5.0/cmd.html#xml-reporting) (Python)
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Once configured, if you create a merge request that triggers a pipeline which collects
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coverage reports, the coverage will be shown in the diff view. This includes reports
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from any job in any stage in the pipeline. The coverage will be displayed for each line:
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- `covered` (green): lines which have been checked at least once by tests
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- `no test coverage` (orange): lines which are loaded but never executed
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- no coverage information: lines which are non-instrumented or not loaded
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Hovering over the coverage bar will provide further information, such as the number
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of times the line was checked by tests.
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## Example test coverage configuration
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The following [`gitlab-ci.yml`](../../../ci/yaml/README.md) example uses [Mocha](https://mochajs.org/)
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JavaScript testing and [NYC](https://github.com/istanbuljs/nyc) coverage-tooling to
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generate the coverage artifact:
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```yaml
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test:
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script:
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- npm install
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- npx nyc --reporter cobertura mocha
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artifacts:
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reports:
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cobertura: coverage/cobertura-coverage.xml
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```
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## Enabling the feature
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This feature comes with the `:coverage_report_view` feature flag disabled by
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default. This feature is disabled due to some performance issues with very large
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data sets. When [the performance issue](https://gitlab.com/gitlab-org/gitlab/issues/37725)
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is resolved, the feature will be enabled by default.
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To enable this feature, ask a GitLab administrator with Rails console access to
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run the following command:
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```ruby
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Feature.enable(:coverage_report_view)
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```
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