public void Log()
{
var engine = new EvaluationEngine();
engine.SetLogExtension(new Log4NetExtension());
engine.Solve <TestQuestion, string>()
.AggregateWithExpressionAggregator(string.Empty, (aggregate, value) => aggregate + value)
.ByEvaluating(question => new TestExpression("one"))
.ByEvaluating(question => new TestExpression("two"));
engine.Answer(new TestQuestion());
this.log4Net.DumpAllMessagesToConsole();
}