How to unit test private methods in BDD / TDD?

Question

I am trying to program according to Behavior Driven Development, which states that no line of code should be written without writing failing unit test first.

My ques

Answer 1

I've been fighting with it for over 1 month, but found the answer:

        var objectOfPrivateMethod = new ObjectOfPrivateMethod(); //yes here is contructor
        object[] arguments = {  }; // here as Object you provide arguments

        var extractedPrivateMethod = typeof(ObjectOfPrivateMethod).GetMethod("Name_Of_Private_Method", BindingFlags.NonPublic|BindingFlags.Static); //if fails returns null. delete flag static if it's not static. Returns your method as an object.
        Assert.AreNotEqual(null, extractedPrivateMethod, "Mathod does not exist"); // good to catch if even exists.

        object result = extractedPrivateMethod.Invoke(null, arguments); // here as object you'll get return value of your function. change null for object of class where is method, if your method is not static 

that's all.