private IExecutionDataSource createValidSource() throws IOException {
File execfile = new File(folder.getRoot(), "test.exec");
OutputStream out = new FileOutputStream(execfile);
ExecutionDataWriter writer = new ExecutionDataWriter(out);
writer.visitSessionInfo(new SessionInfo("id", 1, 2));
writer.visitClassExecution(new ExecutionData(123, "MyClass", 15));
out.close();
return new URLExecutionDataSource(execfile.toURL());
}