def test_function_4 (self) :
     r = collatz_function(555)
     self.assert_(r == 31)
 def test_function_2 (self) :
     r = collatz_function(5)
     self.assert_(r == 6)
 def test_function_3 (self) :
     r = collatz_function(3)
     self.assert_(r == 8)
 def test_function_1 (self) :
     r = collatz_function(1)
     self.assert_(r == 1)