Time Bombs
^^^^^
**Definition:**

* Tests that fail due to ever-so-slightly different time values, during certain days of the week or month, or when a long-running time-sensitive test straddles two hours, days, weeks, months, or years and the code can't handle it.


**Code Example:**

.. code-block:: ruby

  # Subject under test
  require 'bigdecimal'
  require 'bigdecimal/util'

  class TimeCard
    attr_reader :start_time, :end_time

    def initialize(hourly_wage)
      @hourly_wage = hourly_wage
    end

    def punch_in(at = nil)
      @start_time = at || Time.new
    end

    def punch_out(at = nil)
      @end_time = at || Time.new
    end

    def wage_owed
      seconds = (@end_time || Time.new) - @start_time
      hours = seconds / (60 * 60).to_d
      bonus = worked_on_weekend? ? 1.5 : 1

      @hourly_wage * hours * bonus
    end
  end

  # Test
  class TimeBombs < SmellTest
    include UnreliableMinitestPlugin

    def setup
      @subject = TimeCard.new(15)
      @now = Time.new
      super
    end

    def test_punch_in_defaults_to_now
      @subject.punch_in

      assert_equal @subject.start_time.to_ms, @now.to_ms
    end

    def test_calculates_wage_owed
      @subject.punch_in(@now)
      @subject.punch_out(@now + (60 * 60 * 24))

      result = @subject.wage_owed

      assert_equal 360, result.to_i
    end
  end

  # Fake production implementations to simplify example test of subject
  class TimeCard
    def worked_on_weekend?
      return @start_time.wday === 0 ||
        @start_time.wday === 6 ||
        @end_time.wday === 0 ||
        @end_time.wday === 6
    end
  end

**References:**

.. admonition:: Quality attributes

    * :octicon:`file-code;1em` -  Code Example
    * :octicon:`comment-discussion;1em` -  Cause and Effect
    * :octicon:`graph;1em` -  Frequency
    * :octicon:`sync;1em` -  Refactoring

* `A workbook repository of example test smells and what to do about them <https://github.com/testdouble/test-smells>`_ :octicon:`file-code;1em` :octicon:`comment-discussion;1em` :octicon:`sync;1em`
* `Smells in software test code: A survey of knowledge in industry and academia <https://www.sciencedirect.com/science/article/abs/pii/S0164121217303060>`_