最小测试在纯功能上比较脆弱，没有副作用

如何解决最小测试在纯功能上比较脆弱，没有副作用

由于我下周加入了Rails项目（是的！），所以我正在做RomanNumerals kata作为我的工具的精简版，但是我编写的测试随机失败（嘘！）。

• 每次让它们运行时，只要不更改代码，我都会得到不同的结果。
• 我正在使用rails test作为命令。
• 这些版本都是最新版本。来自rails new的所有内容都没有任何其他宝石。 （Ruby 2.7.0，Rails 6.0.3）

在并行运行的测试与一些变量被其他测试覆盖之间似乎有些奇怪的混合。也许有一些奇怪的优化事情涉及到正在进行的缓存？

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,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,0 failures,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

解决方法

我的错误是修改常量。

current_numeral = ROMAN_TEN

current_numeral.prepend(ROMAN_ONE)

我更改了ROMAN_TEN引用的字符串。解决方法是：

ROMAN_TEN = "X".freeze

和

current_numeral = ROMAN_TEN.dup

即使在像这样的小项目上使用rubocop，也会给我警告。