Behavioral challenges in adopting TDD

HI,
 I am anticipating following challenges in TDD adoption. Any suggestion how to deal with such situations?
 

 The list is long :-). Thanks, 
 1.      You have a very experienced, senior and technically sound developer who has designed and developed solutions in a traditional way. This person has not completely bought in to the idea of TDD. How will you motivate such people?  
 2.      The program that you are working on is complex, for that matter every program is complex, has dependencies on other systems/program/modules/components, how and where do you start with TDD? Developer fear making change/refactor as they believe any such attempt can break existing working system. They don't want to mess with something that is working.  
 3.      Your team has traditionally worked in a test after situation, first write code and then write unit test cases. Time and again their mind first think of implementation logic since it has been trained that way for a long time, how do you make them unlearn this habit?  
 4.      TDD will take time initially. The estimation of your project was done when TDD was not in picture. Now that you have to use TDD, how would you now negotiate with your manager and business for this extra time?  
 5.      Why is singleton not considered a good design pattern. what are Technical challenges in using TDD in web applications.  

 

 W
 

 

 An