pythonunittest(8）

将晦涩难懂的测试分解成简单的测试

本篇的目的是解说晦涩的测试不易一目了然，然后用一个例子将晦涩的测试用例化为简单的测试用例，使得测试结果一目了然。

Breaking down obscure tests into simple ones.

Unittest provides the means to test the code through a series of assertions. I have often felt
the temptation to exercise many aspects of a particular piece of code within a single test
method. If any part fails, it becomes obscured as to which part failed. It is preferable to split
things up into several smaller test methods, so that when some part of the code under test
fails, it is obvious.

1. Create a new file named recipe8.py in which to put our application code for this
recipe.

2. Pick a class to test. In this case, we will use an alternative version of the Roman
numeral converter, which converts both ways.

3. Create a new file called recipe8_obscure.py in which to put some longer
test methods.

4. Create some test methods that combine several test assertions.

5. Run the obscure tests. Why did it fail? Where is the bug? It reports that II is not
equal to I, so something appears to be off. If this the only bug?

6. Create another file called recipe8_clear.py to create a more fine-grained set of
test methods.

7. Split up the assertions into separate test methods to give a higher fidelity of output.

8. Run the clearer test suite. Is it a bit clearer where the bug is? What did we trade in to
get this higher degree of test failure? Was it worth the effort?

测试代码1：

# !usr/bin/env python 2.7
# coding: utf-8
# filename: recipe8.py
class RomanNumeralConverter(object):
    def __init__(self):
        self.digit_map = {"M":1000, "D":500, "C":100, "L":50, "X":10, "V":5, "I":1}

    def convert_to_decimal(self, roman_numeral):
        val = 0
        for char in roman_numeral:
            val += self.digit_map[char]
        return val

    def convert_to_roman(self, decimal):
        val = ""
        while decimal > 1000:
            val += "M"
            decimal -= 1000
        while decimal > 500:
            val += "D"
            decimal -= 500
        while decimal > 100:
            val += "C"
            decimal -= 100
        while decimal > 50:
            val += "L"
            decimal -= 50
        while decimal > 10:
            val += "X"
            decimal -= 10
        while decimal > 5:
            val += "V"
            decimal -= 5
        while decimal > 1:
            val += "I"
            decimal -= 1
        return val

# !usr/bin/env python 2.7
# coding: utf-8
# filename: recipe8_obscure.py

import unittest
from recipe8 import *

class RomanNumeralTest(unittest.TestCase):
    def setUp(self):
        self.cvt = RomanNumeralConverter()

    def test_convert_to_decimal(self):
        self.assertEquals(0, self.cvt.convert_to_decimal(""))
        self.assertEquals(1, self.cvt.convert_to_decimal("I"))
        self.assertEquals(2010, \
                          self.cvt.convert_to_decimal("MMX"))
        self.assertEquals(4000, \
                          self.cvt.convert_to_decimal("MMMM"))

    def test_convert_to_roman(self):
        self.assertEquals("", self.cvt.convert_to_roman(0))
        self.assertEquals("II", self.cvt.convert_to_roman(2))
        self.assertEquals("V", self.cvt.convert_to_roman(5))
        self.assertEquals("XII", \
                          self.cvt.convert_to_roman(12))
        self.assertEquals("MMX", \
                          self.cvt.convert_to_roman(2010))
        self.assertEquals("MMMM", \
                          self.cvt.convert_to_roman(4000))

if __name__ == "__main__":
    unittest.main()

结果输出：（这样的结果让人弄不明白倒底哪些用例发生了错误，不如下面用例那样的一目了然）

.F
======================================================================
FAIL: test_convert_to_roman (__main__.RomanNumeralTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "e:\study\python\4668_Code\Chapter 1\01\recipe8_obscure.py", line 22, in test_convert_to_roman
    self.assertEquals("II", self.cvt.convert_to_roman(2))
AssertionError: 'II' != 'I'

----------------------------------------------------------------------
Ran 2 tests in 0.001s

FAILED (failures=1)
Process terminated with an exit code of 1

测试代码2：

# !usr/bin/env python 2.7
# coding: utf-8
# filename: recipe8_clear.py

import unittest
from recipe8 import *

class RomanNumeralTest(unittest.TestCase):
    def setUp(self):
        self.cvt = RomanNumeralConverter()

    def test_to_decimal1(self):
        self.assertEquals(0, self.cvt.convert_to_decimal(""))

    def test_to_decimal2(self):
        self.assertEquals(1, self.cvt.convert_to_decimal("I"))

    def test_to_decimal3(self):
        self.assertEquals(2010, \
                          self.cvt.convert_to_decimal("MMX"))

    def test_to_decimal4(self):
        self.assertEquals(4000, \
                          self.cvt.convert_to_decimal("MMMM"))

    def test_convert_to_roman1(self):
        self.assertEquals("", self.cvt.convert_to_roman(0))

    def test_convert_to_roman2(self):
        self.assertEquals("II", self.cvt.convert_to_roman(2))

    def test_convert_to_roman3(self):
        self.assertEquals("V", self.cvt.convert_to_roman(5))

    def test_convert_to_roman4(self):
        self.assertEquals("XII", \
                          self.cvt.convert_to_roman(12))

    def test_convert_to_roman5(self):
        self.assertEquals("MMX", \
                          self.cvt.convert_to_roman(2010))

    def test_convert_to_roman6(self):
        self.assertEquals("MMMM", \
                          self.cvt.convert_to_roman(4000))

if __name__ == "__main__":
    unittest.main()

结果输出：

.FFFFF....
======================================================================
FAIL: test_convert_to_roman2 (__main__.RomanNumeralTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "e:\study\python\4668_Code\Chapter 1\01\recipe8_clear.py", line 30, in test_convert_to_roman2
    self.assertEquals("II", self.cvt.convert_to_roman(2))
AssertionError: 'II' != 'I'

======================================================================
FAIL: test_convert_to_roman3 (__main__.RomanNumeralTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "e:\study\python\4668_Code\Chapter 1\01\recipe8_clear.py", line 33, in test_convert_to_roman3
    self.assertEquals("V", self.cvt.convert_to_roman(5))
AssertionError: 'V' != 'IIII'

======================================================================
FAIL: test_convert_to_roman4 (__main__.RomanNumeralTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "e:\study\python\4668_Code\Chapter 1\01\recipe8_clear.py", line 37, in test_convert_to_roman4
    self.cvt.convert_to_roman(12))
AssertionError: 'XII' != 'XI'

======================================================================
FAIL: test_convert_to_roman5 (__main__.RomanNumeralTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "e:\study\python\4668_Code\Chapter 1\01\recipe8_clear.py", line 41, in test_convert_to_roman5
    self.cvt.convert_to_roman(2010))
AssertionError: 'MMX' != 'MMVIIII'

======================================================================
FAIL: test_convert_to_roman6 (__main__.RomanNumeralTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "e:\study\python\4668_Code\Chapter 1\01\recipe8_clear.py", line 45, in test_convert_to_roman6
    self.cvt.convert_to_roman(4000))
AssertionError: 'MMMM' != 'MMMDCCCCLXXXXVIIII'

----------------------------------------------------------------------
Ran 10 tests in 0.001s

FAILED (failures=5)
Process terminated with an exit code of 1