Python 如何查找程序中的bug

# coding:utf-8
print('test1')
a = 1
print(a)
print('test2')
b = 2
print(b)
print('test3')
c = 3
print(c)
print('test4')
d = 4
print(d)

print('test5')
def test1():
    print(5)


test1()