doctest -- 註釋裏的單元測試

doctest 是python自帶的模塊， 通過在註釋裏寫代碼，以及結果來進行簡單的測試

def square(x):
    """Squares x.
    >>> square(2)
    4
    >>> square(-2)
    4
    >>> square(5)
    21
    """

    return x * x

doctest.testmod()


**********************************************************************
File "__main__", line 7, in __main__.square
Failed example:
    square(5)
Expected:
    21
Got:
    25
**********************************************************************
1 items had failures:
   1 of   3 in __main__.square
***Test Failed*** 1 failures.
Out[19]:
TestResults(failed=1, attempted=3)

注意>>>後面接測試代碼， 中間有空格，下一行是結果