multiple test files run when I expect only one to run.

[Mitchell L Model]

• Three files: test1.py, test2.py, test3.py
• Each ends with if __name__ == '__main__': result = nose.run()
• I am running these tests in an IDE
• I execute test1.py
• To my surprise the tests in test2.py and test3.py are executed also.

What is happening? How do I avoid it?