Example jenkinsfile to test some arbitrary output in the log

Jenkinsfile

pipeline {
    parameters {
        string(name: 'stuffToCheck', defaultValue: 'Test Failure!,Some Other Failure!', desription: 'CSV of stuff to check in the build-log')
    }
    stages {
        stage('The thing'){
            steps {
                echo 'Test Failure!'
                echo 'Some Other Failure!'
            }
        }
    }
    post {
        always {
            script {
                def stuffToCheck = params.stuffToCheck.tokenize(',')
                def logEntries = currentBuild.rawBuild.getLog(Integer.MAX_VALUE)
                
                def violatingRows = logEntries.findAll { entry -> 
                    stuffToCheck.any { thing -> entry.contains(thing) } 
                }
                if(violatingRows) {
                    error """
                    failing build because of these rows:
                    ======================
                    ${violatingRows.join('\n')}
                    """ 
                } 
            } 
        } 
    }
}