The Python executable is, in my experience, always lowercase "python", so it should probably be:

python SimpleClass.py

You might want to add something about how this can be used
as an aide for unit testing.

This is because when importing, __name__ is the name of the module.

print __name__ # '__main__'
import random
print random.__name__ # 'random'

When random is imported the __name__ == __main__ fails, but when random is executed as a script __name__ == __main__ is true.