Added test for API extension #303
Added test for API extension #303

AngleSharp/AngleSharp,AngleSharp/AngleSharp,FlorianRappl/AngleSharp,FlorianRappl/AngleSharp,FlorianRappl/AngleSharp,AngleSharp/AngleSharp,AngleSharp/AngleSharp,AngleSharp/AngleSharp,FlorianRappl/AngleSharp