Open Test-File as Document to test CompletionProvider

Hi all,

I'm developer for the Netbeans Sightly Extension (http://wcm.io/tooling/netbeans/sightly/) and currently try to cleanup the code and add additional tests.

To test my CompletionProvider classes I'd like to open a local file as javax.swing.text.Document and pass it to my CompletionProvider.

My browsing through the Netbeans Source-Code brought up a solution that should work in my eyes but fails (see below). Is there any chance for me to use local test-files inside my unit-tests through this workflow or am I completely wrong here?
I'd appreciate any suggestions/hints.

Thanks a lot!
Alex

[code]
  public Document getTestDocument(String filename) throws IOException, BadLocationException {
    File file = new File(getClass().getResource("/" + filename).getPath());
    return openDocument(FileUtil.createData(file));
  }

  private Document openDocument(FileObject f) {
    try {
      DataObject dataObject = DataObject.find(f);
      EditorCookie ec = dataObject.getLookup().lookup(EditorCookie.class);
      return ec.openDocument();
    }
    catch (IOException ex) {
      throw new IllegalStateException(ex);
    }
  }
[code]

[code]
java.lang.ExceptionInInitializerError: null
	at org.netbeans.api.project.ProjectManager.<init>(ProjectManager.java:76)
	at org.netbeans.api.project.ProjectManager.<clinit>(ProjectManager.java:70)
	at org.netbeans.modules.projectapi.SimpleFileOwnerQueryImplementation.getOwner(SimpleFileOwnerQueryImplementation.java:161)
	at org.netbeans.api.project.FileOwnerQuery.getOwner(FileOwnerQuery.java:114)
	at org.netbeans.modules.projectapi.ProjectFileEncodingQueryImplementation.getEncoding(ProjectFileEncodingQueryImplementation.java:72)
	at org.netbeans.api.queries.FileEncodingQuery.getEncoding(FileEncodingQuery.java:96)
	at org.openide.text.DataEditorSupport.openDocument(DataEditorSupport.java:584)
	at io.wcm.tooling.netbeans.sightly.completion.BaseTest.openDocument(BaseTest.java:69)
[code][/code]