Coverlet Integration with xUnit in c# | Part - 2

In this blog, i am going to explain following topics. This is my second part of Coverlet Integration with xUnit in c#.  

1. Merging Result
2. Threshold
3. Excluding from Coverage

Merging Result:

With Coverlet, you can combine the output of multiple coverage runs into a single result.

Command used:

dotnet test /p:CollectCoverage=true /p:MergeWith='/path/to/result.json'

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.

In result window we are getting the merge result of code coverage files.

Threshold:

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.

dotnet test /p:CollectCoverage=true /p:Threshold=80

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:

dotnet test /p:CollectCoverage=true /p:Threshold=80 /p:ThresholdType=line

You can specify multiple values for ThresholdType by separating them with commas. Valid values include line, branch and method. You can do the same for Threshold as well.

dotnet test /p:CollectCoverage=true /p:Threshold=\"80,100,70\" /p:ThresholdType=\"line,branch,method\"

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:

Minimum (Default): Ensures the coverage result of each module isn't less than the threshold

Total: Ensures the total combined coverage result of all modules isn't less than the threshold

Average: Ensures the average coverage result of all modules isn't less than the threshold

The following command will compare the threshold value with the overall total coverage of all modules:

dotnet test /p:CollectCoverage=true /p:Threshold=80 /p:ThresholdType=line /p:ThresholdStat=total

Excluding from code coverage:

Attributes:

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.

You can also ignore additional attributes by using the ExcludeByAttribute property (short name, i.e. the type name without the namespace, supported only):

dotnet test /p:CollectCoverage=true /p:ExcludeByAttribute="Obsolete,GeneratedCodeAttribute,CompilerGeneratedAttribute"

Source Files:

You can also ignore specific source files from code coverage using the ExcludeByFile property

Use single or multiple paths (separate by comma)

Use file path or directory path with globbing (e.g dir1/*.cs)

dotnet test /p:CollectCoverage=true /p:ExcludeByFile=\"**/dir1/class1.cs,**/dir2/*.cs,**/dir3/**/*.cs\"

Filters

Coverlet gives the ability to have fine grained control over what gets excluded using "filter expressions".

Syntax: /p:Exclude=[Assembly-Filter]Type-Filter

Wildcards

* => matches zero or more characters

? => the prefixed character is optional

Examples

/p:Exclude="[*]*" => Excludes all types in all assemblies (nothing is instrumented)

/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)

/p:Exclude="[*]Coverlet.Core.Instrumentation.*" => Excludes all types belonging to Coverlet.Core.Instrumentation namespace in any assembly

/p:Exclude="[coverlet.*.tests?]*" => Excludes all types in any assembly starting with coverlet. and ending with .test or .tests (the ? makes the s optional)

/p:Exclude=\"[coverlet.*]*,[*]Coverlet.Core*\" => Excludes assemblies matching coverlet.* and excludes all types belonging to the Coverlet.Core namespace in any assembly

dotnet test /p:CollectCoverage=true /p:Exclude="[coverlet.*]Coverlet.Core.Coverage"

Include:

Coverlet goes a step in the other direction by also letting you explicitly set what can be included using the Include property.

Examples

/p:Include="[*]*" => Includes all types in all assemblies (everything is instrumented)

/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)

/p:Include="[coverlet.*.tests?]*" => Includes all types in any assembly starting with coverlet. and ending with .test or .tests (the ? makes the s optional)

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 (,).

You can also include coverage of the test assembly itself by setting /p:IncludeTestAssembly to true.

For Reference: