/p:MergeWith does not merge but adds

I’m testing using coverlet over a solution that has 3 test projects which i want to combine into a single .opencover.xml file

Since there’s currently no direct solution for this. What I tried to do is generate the coverage for one of the test projects, output its result into an “converage.json” file and then apply a MergeWith param in the following dotnet test commands to merge into that same json file and set the output format to opencover

Problem is, that since the first project(ProjectName.Api) includes other two as references (ProjectName.Application, ProjectName.Data), the report is generated as following:

Test run for /build/test/ProjectName.Api.Tests/bin/Debug/netcoreapp2.0/ProjectName.Api.Tests.dll(.NETCoreApp,Version=v2.0)

Results File: /results/_8e5df6e97674_2018-09-28_11_10_36.trx

Total tests: 15. Passed: 15. Failed: 0. Skipped: 0.
Test Run Successful.
Test execution time: 2.4645 Seconds

Calculating coverage result...
  Generating report '/results/coverage.json'

+----------------------+--------+--------+--------+
| Module               | Line   | Branch | Method |
+----------------------+--------+--------+--------+
|ProjectName.Api         | 24.4%  | 28.6%  | 33.3%  |
+----------------------+--------+--------+--------+
| ProjectName.Data        | 0%     | 0%     | 0%     |
+----------------------+--------+--------+--------+
|ProjectName.Application | 0%     | 0%     | 0%     |
+----------------------+--------+--------+--------+

So it includes two other coverages for the referenced projects with 0% coverage. This wouldn’t be a problem if /p:MergeWith param actually did a proper merge.

But when I run the next dotnet test (over the ProjectName.Application project) with the MergeWith param pointing to this recently generated coverage.json file, I get this:

Test run for /build/test/ProjectName.Application.Tests/bin/Debug/netcoreapp2.0/ProjectName.Application.Tests.dll(.NETCoreApp,Version=v2.0)

Starting test execution, please wait...
Results File: /results/_5d6c3e7d1c85_2018-09-28_11_10_47.trx

Total tests: 4. Passed: 4. Failed: 0. Skipped: 0.
Test Run Successful.
Test execution time: 1.7143 Seconds

Calculating coverage result...
  Generating report '/results/coverage.json'

+----------------------+--------+--------+--------+
| Module               | Line   | Branch | Method |
+----------------------+--------+--------+--------+
| ProjectName.Data        | 0%     | 0%     | 0%     |
+----------------------+--------+--------+--------+
| ProjectName.Application | 100%   | 60%    | 100%   |
+----------------------+--------+--------+--------+
| ProjectName.Api         | 24.4%  | 28.6%  | 33.3%  |
+----------------------+--------+--------+--------+
| ProjectName.Data        | 0%     | 0%     | 0%     |
+----------------------+--------+--------+--------+
| ProjectName.Application | 0%     | 0%     | 0%     |
+----------------------+--------+--------+--------+

So it just adds the recent coverage to the existing ones in coverage.json. Causing a duplicated coverage in ProjectName.Application and ProjectName.Data (because again, ProjectName.Application references ProjectName.Data, so it adds a coverage 0% report)

Any solutions to this? Or am I missusing something?

Or even a way for coverlet for avoid including referenced project coverage?

[Dragon160]

Any update here? I think it is quite a common use case to have more than one test project within the solution. A way to aggregate it so a single output would be really nice.

[tonerdo]

Definitely sounds like a good idea @vlef @pape77. For starters I could just make the MergeWith parameter ignore when the specified file doesn’t exist and just assume it’s on a first run