Try using a JUnit Formatter Elixir package together with the junit pipeline step in your Jenkinsfile.

I have tested both suggestions.

@shanesveller This solution works and is quite nice. It forces me to change the test_helper.exs but that is a minor inconvenience overall. It is nice but it only offers the most basic of reports and for me this is where it fails.

@hauleth The option I decided to go with. Yes, making the Jenkinsfile work for Cobertura was a nightmare, specially because in previous versions it was not even possible and because there contradictory information scattered all over the place.

However, once you get that Jenkinsfile going, you get to rip those sweet reports from Cobertura. Cobertura was made with Java in mind, there is no two ways about it. In the reports you see things like Class coverage and such, but you can easily translate that do modules. The interface offers a lot more information and tracks coverage over time, which is something I actually want.

For future notice, here is my Jenkinsfile:

pipeline {
  agent any

  environment { 
    SOME_VAR = "/home/deployer"
  }

  stages {
    stage("Build") {
      steps {
        sh "MIX_ENV=test mix do deps.get, deps.compile"
      }
    }

    stage("Test") {
      steps {
        sh "mix test --cover"
      }
    }

    stage("Credo"){
      steps{
        sh "mix credo --strict"
      }
    }

    stage("Deploy"){
      when{
        expression{
          env.BRANCH_NAME == "master"
        }
      }
      steps{
        sh '''
         echo "Deploy with AWS or GCP or whatever"                                                         
        '''
      }
    }

  }

  post{
    always{
      cobertura coberturaReportFile: "coverage.xml"
    }
  }
}

Of notice:

1. I am extremely Nazi with my code, so I also use Credo. You can further configure it as to not blow the entire pipeline because you missed a new line at the end of file but as I said, I am quite Nazi with my code.
2. The Deploy stage only runs if the pushed branch is Master. There are other ways of doing this, but I found it that having this way for a small project was good enough.

Overall I like covertools for now but I don’t know if the first solution has the same potential. At least I didn’t see it.

Hope this post helps!