pythonunittest(9）

测试边界条件

Testing the edges
When we write automated tests, we pick the inputs and assert the expected outputs. It is
important to test the limits of the inputs to make sure our code can handle good and bad
inputs. This is also known as testing corner cases.

1. Create a new file named recipe9.py in which to put all our code for this recipe.

2. Pick a class to test. In this recipe, we'll use another variation of our Roman numeral
converter. This one doesn't process values greater than 4000.

3. Create a test case that sets up an instance of the Roman numeral converter.

4. Add several test methods that exercise the edges of converting to Roman numeral
notation.

5. Add several test methods that exercise the edges of converting to decimal notation.

6. Add some tests that exercise the tiers of converting decimals to Roman numerals.

7. Add some tests that input unexpected values to the Roman numeral converter.

8. Add a unit test runner.

测试代码：

# !usr/bin/env python 2.7
# coding: utf-8
# filename: recipe9.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]
        if val > 4000:
            raise Exception("We don't handle values over 4000")
        return val

    def convert_to_roman(self, decimal):
        if decimal > 4000:
            raise Exception("We don't handle values over 4000")
        val = ""
        mappers = [(1000,"M"), (500,"D"), (100,"C"), (50,"L"), (10,"X"), (5,"V"), (1,"I")]
        for (mapper_dec, mapper_rom) in mappers:
            while decimal >= mapper_dec:
                val += mapper_rom
                decimal -= mapper_dec
        return val

import unittest

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

    def test_to_roman_bottom(self):
        self.assertEquals("I", self.cvt.convert_to_roman(1))

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

    def test_to_roman_negative_value(self):
        self.assertEquals("", self.cvt.convert_to_roman(-1))

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

    def test_to_roman_above_top(self):
        self.assertRaises(Exception, \
                          self.cvt.convert_to_roman, 4001)

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

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

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

    def test_to_decimal_above_top(self):
        self.assertRaises(Exception, \
                         self.cvt.convert_to_decimal, "MMMMI")

    def test_to_roman_tier1(self):
        self.assertEquals("V", self.cvt.convert_to_roman(5))

    def test_to_roman_tier2(self):
        self.assertEquals("X", self.cvt.convert_to_roman(10))

    def test_to_roman_tier3(self):
        self.assertEquals("L", self.cvt.convert_to_roman(50))

    def test_to_roman_tier4(self):
        self.assertEquals("C", self.cvt.convert_to_roman(100))

    def test_to_roman_tier5(self):
        self.assertEquals("D", self.cvt.convert_to_roman(500))

    def test_to_roman_tier6(self):
        self.assertEquals("M", \
                          self.cvt.convert_to_roman(1000))

    def test_to_roman_bad_inputs(self):
        self.assertEquals("", self.cvt.convert_to_roman(None))
        self.assertEquals("I", self.cvt.convert_to_roman(1.2))

    def test_to_decimal_bad_inputs(self):
        self.assertRaises(TypeError, \
                          self.cvt.convert_to_decimal, None)
        self.assertRaises(TypeError, \
                          self.cvt.convert_to_decimal, 1.2)

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

结果输出：

.................
----------------------------------------------------------------------
Ran 17 tests in 0.000s

OK

注意类似这样的代码：

    
    def test_to_roman_above_top(self):
        self.assertRaises(Exception, \
                          self.cvt.convert_to_roman, 4001)

用于捕获程序中的异常