public void FillTest()
{
Document doc = new Document();
doc.Fill(
Width => 100,
Height => 200,
Attributes => new Pairs{ attr1 => 1,
attr2 => 2 });
Assert.AreEqual(100, (int)doc["Width"]);
Assert.AreEqual(200, (int)doc["Height"]);
Assert.IsInstanceOfType(doc["Attributes"], typeof(Document));
}