Toni Solarin-Sodara
209 lines
10 KiB
Markdown
209 lines
10 KiB
Markdown
# Coverlet integration with MSBuild
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In this mode, Coverlet doesn't require any additional setup other than including the NuGet package in the unit test project. It integrates with the `dotnet test` infrastructure built into the .NET Core CLI and when enabled, will automatically generate coverage results after tests are run.
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If a property takes multiple comma-separated values please note that [you will have to add escaped quotes around the string](https://github.com/Microsoft/msbuild/issues/2999#issuecomment-366078677) like this: `/p:Exclude=\"[coverlet.*]*,[*]Coverlet.Core*\"`, `/p:Include=\"[coverlet.*]*,[*]Coverlet.Core*\"`, or `/p:CoverletOutputFormat=\"json,opencover\"`.
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## Code Coverage
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Enabling code coverage is as simple as setting the `CollectCoverage` property to `true`
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```bash
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dotnet test /p:CollectCoverage=true
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```
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After the above command is run, a `coverage.json` file containing the results will be generated in the root directory of the test project. A summary of the results will also be displayed in the terminal.
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## Coverage Output
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Coverlet can generate coverage results in multiple formats, which is specified using the `CoverletOutputFormat` property. For example, the following command emits coverage results in the `opencover` format:
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```bash
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dotnet test /p:CollectCoverage=true /p:CoverletOutputFormat=opencover
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```
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Supported Formats:
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* json (default)
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* lcov
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* opencover
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* cobertura
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* teamcity
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You can specify multiple output formats by separating them with a comma (`,`).
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The output of the coverage result can be specified using the `CoverletOutput` property.
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```bash
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dotnet test /p:CollectCoverage=true /p:CoverletOutput='./result.json'
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```
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To specify a directory where all results will be written to (especially if using multiple formats), end the value with a `/`.
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```bash
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dotnet test /p:CollectCoverage=true /p:CoverletOutput='./results/'
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```
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The Coverlet MSBuild task sets the `CoverletReport` MSBuild item so that you can easily use the produced coverage reports. For example, using [ReportGenerator](https://github.com/danielpalme/ReportGenerator#usage--command-line-parameters) to generate an html coverage report.
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```xml
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<Target Name="GenerateHtmlCoverageReport" AfterTargets="GenerateCoverageResultAfterTest">
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<ReportGenerator ReportFiles="@(CoverletReport)" TargetDirectory="../html-coverage-report" />
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</Target>
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```
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### TeamCity Output
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Coverlet can output basic code coverage statistics using [TeamCity service messages](https://confluence.jetbrains.com/display/TCD18/Build+Script+Interaction+with+TeamCity#BuildScriptInteractionwithTeamCity-ServiceMessages).
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```bash
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dotnet test /p:CollectCoverage=true /p:CoverletOutputFormat=teamcity
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```
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The currently supported [TeamCity statistics](https://confluence.jetbrains.com/display/TCD18/Build+Script+Interaction+with+TeamCity#BuildScriptInteractionwithTeamCity-ServiceMessages) are:
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| TeamCity Statistic Key | Description |
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|:------------------------|:-------------------------------|
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| CodeCoverageL | Line-level code coverage |
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| CodeCoverageB | Branch-level code coverage |
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| CodeCoverageM | Method-level code coverage |
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| CodeCoverageAbsLTotal | The total number of lines |
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| CodeCoverageAbsLCovered | The number of covered lines |
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| CodeCoverageAbsBTotal | The total number of branches |
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| CodeCoverageAbsBCovered | The number of covered branches |
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| CodeCoverageAbsMTotal | The total number of methods |
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| CodeCoverageAbsMCovered | The number of covered methods |
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## Merging Results
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With Coverlet, you can combine the output of multiple coverage runs into a single result.
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```bash
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dotnet test /p:CollectCoverage=true /p:MergeWith='/path/to/result.json'
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```
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The value given to `/p:MergeWith` **must** be a path to Coverlet's own json result format. The results in `result.json` will be read, and added to the new results written to by Coverlet. [Check the sample](Examples.md).
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## Threshold
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Coverlet allows you to specify a coverage threshold below which it fails the build. This allows you to enforce a minimum coverage percent on all changes to your project.
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```bash
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dotnet test /p:CollectCoverage=true /p:Threshold=80
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```
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The above command will automatically fail the build if the line, branch or method coverage of _any_ of the instrumented modules falls below 80%. You can specify what type of coverage to apply the threshold value to using the `ThresholdType` property. For example to apply the threshold check to only **line** coverage:
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```bash
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dotnet test /p:CollectCoverage=true /p:Threshold=80 /p:ThresholdType=line
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```
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You can specify multiple values for `ThresholdType` by separating them with commas. Valid values include `line`, `branch` and `method`.
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By default, Coverlet will validate the threshold value against the coverage result of each module. The `/p:ThresholdStat` option allows you to change this behaviour and can have any of the following values:
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* Minimum (Default): Ensures the coverage result of each module isn't less than the threshold
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* Total: Ensures the total combined coverage result of all modules isn't less than the threshold
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* Average: Ensures the average coverage result of all modules isn't less than the threshold
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The following command will compare the threshold value with the overall total coverage of all modules:
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```bash
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dotnet test /p:CollectCoverage=true /p:Threshold=80 /p:ThresholdType=line /p:ThresholdStat=total
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```
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## Excluding From Coverage
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### Attributes
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You can ignore a method, an entire class or assembly from code coverage by creating and applying the `ExcludeFromCodeCoverage` attribute present in the `System.Diagnostics.CodeAnalysis` namespace.
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You can also ignore additional attributes by using the `ExcludeByAttribute` property (short name, i.e. the type name without the namespace, supported only):
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```bash
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dotnet test /p:CollectCoverage=true /p:ExcludeByAttribute="Obsolete,GeneratedCodeAttribute,CompilerGeneratedAttribute"
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```
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### Source Files
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You can also ignore specific source files from code coverage using the `ExcludeByFile` property
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- Use single or multiple paths (separate by comma)
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- Use file path or directory path with globbing (e.g `dir1/*.cs`)
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```bash
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dotnet test /p:CollectCoverage=true /p:ExcludeByFile=\"**/dir1/class1.cs,**/dir2/*.cs,**/dir3/**/*.cs\"
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```
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### Filters
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Coverlet gives the ability to have fine grained control over what gets excluded using "filter expressions".
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Syntax: `/p:Exclude=[Assembly-Filter]Type-Filter`
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Wildcards
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- `*` => matches zero or more characters
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- `?` => the prefixed character is optional
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Examples
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- `/p:Exclude="[*]*"` => Excludes all types in all assemblies (nothing is instrumented)
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- `/p:Exclude="[coverlet.*]Coverlet.Core.Coverage"` => Excludes the Coverage class in the `Coverlet.Core` namespace belonging to any assembly that matches `coverlet.*` (e.g `coverlet.core`)
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- `/p:Exclude="[*]Coverlet.Core.Instrumentation.*"` => Excludes all types belonging to `Coverlet.Core.Instrumentation` namespace in any assembly
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- `/p:Exclude="[coverlet.*.tests?]*"` => Excludes all types in any assembly starting with `coverlet.` and ending with `.test` or `.tests` (the `?` makes the `s` optional)
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- `/p:Exclude=\"[coverlet.*]*,[*]Coverlet.Core*\"` => Excludes assemblies matching `coverlet.*` and excludes all types belonging to the `Coverlet.Core` namespace in any assembly
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```bash
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dotnet test /p:CollectCoverage=true /p:Exclude="[coverlet.*]Coverlet.Core.Coverage"
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```
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Coverlet goes a step in the other direction by also letting you explicitly set what can be included using the `Include` property.
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Examples
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- `/p:Include="[*]*"` => Includes all types in all assemblies (everything is instrumented)
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- `/p:Include="[coverlet.*]Coverlet.Core.Coverage"` => Includes the Coverage class in the `Coverlet.Core` namespace belonging to any assembly that matches `coverlet.*` (e.g `coverlet.core`)
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- `/p:Include="[coverlet.*.tests?]*"` => Includes all types in any assembly starting with `coverlet.` and ending with `.test` or `.tests` (the `?` makes the `s` optional)
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Both `Exclude` and `Include` properties can be used together but `Exclude` takes precedence. You can specify multiple filter expressions by separting them with a comma (`,`).
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You can also include coverage of the test assembly itself by setting `/p:IncludeTestAssembly` to `true`.
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### Skip auto-implemented properties
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Neither track nor record auto-implemented properties.
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Syntax: `/p:SkipAutoProps=true`
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### Methods that do not return
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Methods that do not return can be marked with attributes to cause statements after them to be excluded from coverage. `DoesNotReturnAttribute` is included by default.
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Attributes can be specified with the following syntax.
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Syntax: `/p:DoesNotReturnAttribute="DoesNotReturnAttribute,OtherAttribute"`
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### Note for Powershell / Azure DevOps users
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To exclude or include multiple assemblies when using Powershell scripts or creating a .yaml file for an Azure DevOps build ```%2c``` should be used as a separator. Msbuild will translate this symbol to ```,```.
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```/p:Exclude="[*]*Examples?%2c[*]*Startup"```
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Azure DevOps builds do not require double quotes to be unescaped:
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```
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dotnet test --configuration $(buildConfiguration) --no-build /p:CollectCoverage=true /p:CoverletOutputFormat=cobertura /p:CoverletOutput=$(Build.SourcesDirectory)/TestResults/Coverage/ /p:Exclude="[MyAppName.DebugHost]*%2c[MyAppNamet.WebHost]*%2c[MyAppName.App]*"
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```
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### Note for Linux users
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[There is an issue with MSBuild on Linux](https://github.com/microsoft/msbuild/issues/3468) that affects the ability to escape quotes while specifying multiple comma-separated values. Linux MSBuild automatically translates `\` to `/` in properties, tasks, etc. before using them, which means if you specified `/p:CoverletOutputFormat=\"json,opencover\"` in an MSBuild script, it will be converted to `/p:CoverletOutputFormat=/"json,opencover/"` before execution. This yields an error similar to the following:
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```text
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MSBUILD : error MSB1006: Property is not valid. [/home/vsts/work/1/s/default.proj]
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Switch: opencover/
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```
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You'll see this if directly consuming Linux MSBuild or if using the Azure DevOps `MSBuild` task on a Linux agent.
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The workaround is to use the .NET Core `dotnet msbuild` command instead of using MSBuild directly. The issue is not present in `dotnet msbuild` and the script will run with correctly escaped quotes.
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## SourceLink
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Coverlet supports [SourceLink](https://github.com/dotnet/sourcelink) custom debug information contained in PDBs. When you specify the `/p:UseSourceLink=true` property, Coverlet will generate results that contain the URL to the source files in your source control instead of local file paths.
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