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ruby-on-rails - Minitests 在纯函数上很不稳定，没有副作用

问题描述

我正在做一个 RomanNumerals kata 作为我的工具的调整，因为我下周将加入一个 Rails 项目（耶！），但我编写的测试随机失败（嘘！）。

并行运行的测试和一些变量被其他测试覆盖之间似乎有些奇怪的混合。或者也许有一些奇怪的优化事情涉及缓存？


Running via Spring preloader in process 18166
Run options: --seed 29967

# Running:

.......F

Failure:
RomanNumeralHelperTest#test_18_returns_XVIII [/home/eric/rails/rome/test/helpers/roman_numeral_helper_test.rb:55]:
Expected: "XVIII"
  Actual: "IXVIII"


rails test test/helpers/roman_numeral_helper_test.rb:54

........

Finished in 0.066531s, 240.4883 runs/s, 240.4883 assertions/s.
16 runs, 16 assertions, 1 failures, 0 errors, 0 skips

Running via Spring preloader in process 18195
Run options: --seed 59433

# Running:

.............F

Failure:
RomanNumeralHelperTest#test_15_returns_XV [/home/eric/rails/rome/test/helpers/roman_numeral_helper_test.rb:51]:
Expected: "XV"
  Actual: "IXV"


rails test test/helpers/roman_numeral_helper_test.rb:50

..

Finished in 0.053298s, 300.2008 runs/s, 300.2008 assertions/s.
16 runs, 16 assertions, 1 failures, 0 errors, 0 skips

Running via Spring preloader in process 18247
Run options: --seed 14645

# Running:

................

Finished in 0.048711s, 328.4691 runs/s, 328.4691 assertions/s.
16 runs, 16 assertions, 0 failures, 0 errors, 0 skips

class RomanNumeralHelperTest < ActiveSupport::TestCase
  test "1 returns I" do
    assert_equal "I", RomanNumeralHelper.convert(1)
  end  

  test "2 returns II" do
    assert_equal "II", RomanNumeralHelper.convert(2)
  end  
  
  test "3 returns III" do
    assert_equal "III", RomanNumeralHelper.convert(3)
  end

  # Intermittent tests omitted. They go from 1 to 20.

  test "20 returns XX" do
    assert_equal "XX", RomanNumeralHelper.convert(20)
  end
end

module RomanNumeralHelper
  ROMAN_ONE = "I"
  ROMAN_FIVE = "V"
  ROMAN_TEN = "X"
  def self.convert(number)
    result = ""
    current_numeral = ""
    remaining_number = number    

    until remaining_number == 0 do
      if remaining_number > 8
        current_numeral = ROMAN_TEN
        remaining_number -= 10
      elsif remaining_number > 3
        current_numeral += ROMAN_FIVE
        remaining_number -= 5
      else
        result += ROMAN_ONE * remaining_number
        remaining_number = 0
      end      
      if remaining_number < 0
        current_numeral.prepend(ROMAN_ONE)
        remaining_number = 0
      end      

      result += current_numeral
      current_numeral = ""
    end    

    result
  end
end

标签： ruby-on-railsrubyminitest

解决方案

我的错误是修改了一个常量。

current_numeral = ROMAN_TEN

current_numeral.prepend(ROMAN_ONE)

我更改了 ROMAN_TEN 引用的字符串。修复方法是：

ROMAN_TEN = "X".freeze

和

current_numeral = ROMAN_TEN.dup

同样使用 rubocop - 即使在像这样的小项目中 - 也会给我一个警告。

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