Try cleaning

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@@ -6,9 +6,8 @@ pipeline {
                script {
                   def customImage = docker.build("paper-cutter:${env.BUILD_ID}")
                   customImage.inside() {
+                      cleanWs()
                       dir('test') {
-                          sh 'git clone https://git.wmi.amu.edu.pl/filipg/paper-cutter.git'
-                          sh 'ls -l paper-cutter'
                          sh 'bash run_tests.sh'
                       }
                   }