Use Oracle JVM Use a non-US locale in OS (tested with ES -spanish). clone windup repository, or pull latest upstream. Execute mvn clean install Expected behavior: all tests finishes succesfully. Actual behavior: 1 tests fails: Results : Tests in error: WindupArchitectureSourceModeTest.testRunWindupSourceMode:110->validateReports:277 » NotFoundException_$$_javassist_afa33a49-0767-4317-bac7-92a05cb0a937 Tests run: 109, Failures: 0, Errors: 1, Skipped: 1 Searching for the test in test/target/surefire-reports : ------------------------------------------------------------------------------- Test set: org.jboss.windup.tests.application.WindupArchitectureMediumBinaryModeTest ------------------------------------------------------------------------------- Tests run: 2, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 433.473 sec <<< FAILURE! - in org.jboss.windup.tests.application.WindupArchitectureMediumBinaryModeTest testRunWindupMediumWithFernflower(org.jboss.windup.tests.application.WindupArchitectureMediumBinaryModeTest) Time elapsed: 235.797 sec <<< ERROR! org.javassist.tmp.java.lang.RuntimeException_$$_javassist_48493df8-3e6e-48c3-b25c-a78471be3baf: Effort: 2.210 could not be parsed as numeric! at org.jboss.windup.tests.application.WindupArchitectureMediumBinaryModeTest.validateOverviewReport(WindupArchitectureMediumBinaryModeTest.java:163) at org.jboss.windup.tests.application.WindupArchitectureMediumBinaryModeTest.validateReports(WindupArchitectureMediumBinaryModeTest.java:189) at org.jboss.windup.tests.application.WindupArchitectureMediumBinaryModeTest.testRunWindupMediumWithFernflower(WindupArchitectureMediumBinaryModeTest.java:63)