导航:起始页 > Dive Into Python > 重构 > 应对需求变化 | << >> | ||||
深入 Python :Dive Into Python 中文版Python 从新手到专家 [Dip_5.4b_CPyUG_Release] |
尽管你竭尽努力地分析你的客户,并点灯熬油地提炼出精确的需求,但需求还是会是不断变化。大部分客户在看到产品前不知道他们想要什么。即便知道,也不擅于精确表述出他们的有效需求。即便能表述出来,他们在下一个版本一定会要求更多的功能。因此你需要做好更新测试用例的准备以应对需求的改变。
假设你想要扩展罗马数字转换函数的范围。还记得没有哪个字符可以重复三遍以上这条规则吗?呃,现在罗马人希望给这条规则来个例外,用连续出现 4 个 M 字符来表示 4000。如果这样改了,你就可以把转换范围从 1..3999 扩展到 1..4999。但你先要对测试用例进行修改。
这个文件可以在例子目录下的 py/roman/stage7/ 目录中找到。
如果您还没有下载本书附带的样例程序, 可以 下载本程序和其他样例程序。
import roman71 import unittest class KnownValues(unittest.TestCase): knownValues = ( (1, 'I'), (2, 'II'), (3, 'III'), (4, 'IV'), (5, 'V'), (6, 'VI'), (7, 'VII'), (8, 'VIII'), (9, 'IX'), (10, 'X'), (50, 'L'), (100, 'C'), (500, 'D'), (1000, 'M'), (31, 'XXXI'), (148, 'CXLVIII'), (294, 'CCXCIV'), (312, 'CCCXII'), (421, 'CDXXI'), (528, 'DXXVIII'), (621, 'DCXXI'), (782, 'DCCLXXXII'), (870, 'DCCCLXX'), (941, 'CMXLI'), (1043, 'MXLIII'), (1110, 'MCX'), (1226, 'MCCXXVI'), (1301, 'MCCCI'), (1485, 'MCDLXXXV'), (1509, 'MDIX'), (1607, 'MDCVII'), (1754, 'MDCCLIV'), (1832, 'MDCCCXXXII'), (1993, 'MCMXCIII'), (2074, 'MMLXXIV'), (2152, 'MMCLII'), (2212, 'MMCCXII'), (2343, 'MMCCCXLIII'), (2499, 'MMCDXCIX'), (2574, 'MMDLXXIV'), (2646, 'MMDCXLVI'), (2723, 'MMDCCXXIII'), (2892, 'MMDCCCXCII'), (2975, 'MMCMLXXV'), (3051, 'MMMLI'), (3185, 'MMMCLXXXV'), (3250, 'MMMCCL'), (3313, 'MMMCCCXIII'), (3408, 'MMMCDVIII'), (3501, 'MMMDI'), (3610, 'MMMDCX'), (3743, 'MMMDCCXLIII'), (3844, 'MMMDCCCXLIV'), (3888, 'MMMDCCCLXXXVIII'), (3940, 'MMMCMXL'), (3999, 'MMMCMXCIX'), (4000, 'MMMM'), (4500, 'MMMMD'), (4888, 'MMMMDCCCLXXXVIII'), (4999, 'MMMMCMXCIX')) def testToRomanKnownValues(self): """toRoman should give known result with known input""" for integer, numeral in self.knownValues: result = roman71.toRoman(integer) self.assertEqual(numeral, result) def testFromRomanKnownValues(self): """fromRoman should give known result with known input""" for integer, numeral in self.knownValues: result = roman71.fromRoman(numeral) self.assertEqual(integer, result) class ToRomanBadInput(unittest.TestCase): def testTooLarge(self): """toRoman should fail with large input""" self.assertRaises(roman71.OutOfRangeError, roman71.toRoman, 5000) def testZero(self): """toRoman should fail with 0 input""" self.assertRaises(roman71.OutOfRangeError, roman71.toRoman, 0) def testNegative(self): """toRoman should fail with negative input""" self.assertRaises(roman71.OutOfRangeError, roman71.toRoman, -1) def testNonInteger(self): """toRoman should fail with non-integer input""" self.assertRaises(roman71.NotIntegerError, roman71.toRoman, 0.5) class FromRomanBadInput(unittest.TestCase): def testTooManyRepeatedNumerals(self): """fromRoman should fail with too many repeated numerals""" for s in ('MMMMM', 'DD', 'CCCC', 'LL', 'XXXX', 'VV', 'IIII'): self.assertRaises(roman71.InvalidRomanNumeralError, roman71.fromRoman, s) def testRepeatedPairs(self): """fromRoman should fail with repeated pairs of numerals""" for s in ('CMCM', 'CDCD', 'XCXC', 'XLXL', 'IXIX', 'IVIV'): self.assertRaises(roman71.InvalidRomanNumeralError, roman71.fromRoman, s) def testMalformedAntecedent(self): """fromRoman should fail with malformed antecedents""" for s in ('IIMXCC', 'VX', 'DCM', 'CMM', 'IXIV', 'MCMC', 'XCX', 'IVI', 'LM', 'LD', 'LC'): self.assertRaises(roman71.InvalidRomanNumeralError, roman71.fromRoman, s) def testBlank(self): """fromRoman should fail with blank string""" self.assertRaises(roman71.InvalidRomanNumeralError, roman71.fromRoman, "") class SanityCheck(unittest.TestCase): def testSanity(self): """fromRoman(toRoman(n))==n for all n""" for integer in range(1, 5000): numeral = roman71.toRoman(integer) result = roman71.fromRoman(numeral) self.assertEqual(integer, result) class CaseCheck(unittest.TestCase): def testToRomanCase(self): """toRoman should always return uppercase""" for integer in range(1, 5000): numeral = roman71.toRoman(integer) self.assertEqual(numeral, numeral.upper()) def testFromRomanCase(self): """fromRoman should only accept uppercase input""" for integer in range(1, 5000): numeral = roman71.toRoman(integer) roman71.fromRoman(numeral.upper()) self.assertRaises(roman71.InvalidRomanNumeralError, roman71.fromRoman, numeral.lower()) if __name__ == "__main__": unittest.main()
现在你的测试用例和新需求保持一致了,但是你的程序代码还没有,因此几个测试用例的失败是意料之中的事。
fromRoman should only accept uppercase input ... ERROR toRoman should always return uppercase ... ERROR fromRoman should fail with blank string ... ok fromRoman should fail with malformed antecedents ... ok fromRoman should fail with repeated pairs of numerals ... ok fromRoman should fail with too many repeated numerals ... ok fromRoman should give known result with known input ... ERROR toRoman should give known result with known input ... ERROR fromRoman(toRoman(n))==n for all n ... ERROR toRoman should fail with non-integer input ... ok toRoman should fail with negative input ... ok toRoman should fail with large input ... ok toRoman should fail with 0 input ... ok
====================================================================== ERROR: fromRoman should only accept uppercase input ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage7\romantest71.py", line 161, in testFromRomanCase numeral = roman71.toRoman(integer) File "roman71.py", line 28, in toRoman raise OutOfRangeError, "number out of range (must be 1..3999)" OutOfRangeError: number out of range (must be 1..3999) ====================================================================== ERROR: toRoman should always return uppercase ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage7\romantest71.py", line 155, in testToRomanCase numeral = roman71.toRoman(integer) File "roman71.py", line 28, in toRoman raise OutOfRangeError, "number out of range (must be 1..3999)" OutOfRangeError: number out of range (must be 1..3999) ====================================================================== ERROR: fromRoman should give known result with known input ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage7\romantest71.py", line 102, in testFromRomanKnownValues result = roman71.fromRoman(numeral) File "roman71.py", line 47, in fromRoman raise InvalidRomanNumeralError, 'Invalid Roman numeral: %s' % s InvalidRomanNumeralError: Invalid Roman numeral: MMMM ====================================================================== ERROR: toRoman should give known result with known input ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage7\romantest71.py", line 96, in testToRomanKnownValues result = roman71.toRoman(integer) File "roman71.py", line 28, in toRoman raise OutOfRangeError, "number out of range (must be 1..3999)" OutOfRangeError: number out of range (must be 1..3999) ====================================================================== ERROR: fromRoman(toRoman(n))==n for all n ---------------------------------------------------------------------- Traceback (most recent call last): File "C:\docbook\dip\py\roman\stage7\romantest71.py", line 147, in testSanity numeral = roman71.toRoman(integer) File "roman71.py", line 28, in toRoman raise OutOfRangeError, "number out of range (must be 1..3999)" OutOfRangeError: number out of range (must be 1..3999) ---------------------------------------------------------------------- Ran 13 tests in 2.213s FAILED (errors=5)
既然新的需求导致了测试用例的失败,你该考虑修改代码以便它能再次通过测试用例。(在你开始编写单元测试时要习惯一件事:被测试代码永远不会在编写测试用例“之前”编写。正因为如此,你还有一些工作要做,一旦可以通过所有的测试用例,停止编码。)
这个文件可以在例子目录下的 py/roman/stage7/ 目录中找到。
"""Convert to and from Roman numerals""" import re #Define exceptions class RomanError(Exception): pass class OutOfRangeError(RomanError): pass class NotIntegerError(RomanError): pass class InvalidRomanNumeralError(RomanError): pass #Define digit mapping romanNumeralMap = (('M', 1000), ('CM', 900), ('D', 500), ('CD', 400), ('C', 100), ('XC', 90), ('L', 50), ('XL', 40), ('X', 10), ('IX', 9), ('V', 5), ('IV', 4), ('I', 1)) def toRoman(n): """convert integer to Roman numeral""" if not (0 < n < 5000): raise OutOfRangeError, "number out of range (must be 1..4999)" if int(n) <> n: raise NotIntegerError, "non-integers can not be converted" result = "" for numeral, integer in romanNumeralMap: while n >= integer: result += numeral n -= integer return result #Define pattern to detect valid Roman numerals romanNumeralPattern = '^M?M?M?M?(CM|CD|D?C?C?C?)(XC|XL|L?X?X?X?)(IX|IV|V?I?I?I?)$' def fromRoman(s): """convert Roman numeral to integer""" if not s: raise InvalidRomanNumeralError, 'Input can not be blank' if not re.search(romanNumeralPattern, s): raise InvalidRomanNumeralError, 'Invalid Roman numeral: %s' % s result = 0 index = 0 for numeral, integer in romanNumeralMap: while s[index:index+len(numeral)] == numeral: result += integer index += len(numeral) return result
你可能会怀疑只需这两处小改动。嘿,不相信我的话,你自己看看吧:
fromRoman should only accept uppercase input ... ok toRoman should always return uppercase ... ok fromRoman should fail with blank string ... ok fromRoman should fail with malformed antecedents ... ok fromRoman should fail with repeated pairs of numerals ... ok fromRoman should fail with too many repeated numerals ... ok fromRoman should give known result with known input ... ok toRoman should give known result with known input ... ok fromRoman(toRoman(n))==n for all n ... ok toRoman should fail with non-integer input ... ok toRoman should fail with negative input ... ok toRoman should fail with large input ... ok toRoman should fail with 0 input ... ok ---------------------------------------------------------------------- Ran 13 tests in 3.685s OK
全面的单元测试意味着不必依赖于程序员的一面之词:“相信我!”
<< 重构 |
| 1 | 2 | 3 | 4 | 5 | |
重构 >> |