Error generating web.xml file with IntelliJ IDEA

If you use IntelliJ IDEA for your Grails development you might encounter this error running integration tests:

Error Error generating web.xml file (Use --stacktrace to see the full trace)

The reason for this is that IDEA adds classpath by default on creating integration test run configuration. Unfortunately, sometimes it causes strange errors like this one. Follow these steps to resolve:

1. Open Run → Edit Configurations... (or press Alt+Shift+F10)
2. Select your configuration that fails
3. Uncheck Add --classpath checkbox
4. You are done! Run.