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def age
  (Date.today - self.dob).to_i / 365.25
end

Posted in Test Driven Development, Ruby on Rails | Tags dates, testing | 6 comments

Comments

1. nukeedit
   Lewis said about 18 hours later:
   

   There is a bug in the code.

   For example: dob = 1/1/2005 the day before is 12/31/2004

   so 2004 – 2005 = -1

   My birthday happens to be on the 1st of January :)

2. nukeedit
   Doug said about 20 hours later:
   

   Good catch! Although I don’t know that it’s a bug as much as just undefined. When I posed the question I never said what I wanted to happen with birthdays in the future. It could be argued that your age (given your birthday is in the future) is negative. :-) Ether way, I’ved added a result = 0 if result < 0 statement in age_in_years and these test cases:

       @born.dob=Date.parse("Jan 1, 2005")
       assert_equal 0, @born.age(Date.parse("Jan 2, 2005"))
       assert_equal 0, @born.age(Date.parse("Dec 31, 2005"))
       assert_equal 1, @born.age(Date.parse("Jan 2, 2006"))
       assert_equal 0, @born.age(Date.parse("Dec 31, 2004"))

   The format of these tests are a little different than Jim’s because of my environment.

3. nukeedit
   Jim Weirich said about 20 hours later:
   

   Hi Lewis,

   I don’t see a bug involving the first of January. In fact, I added this test case to make sure:

   def test_lewis_birthday
     born = Date.parse("Jan 1, 2005")
     assert_equal 0, age_in_years(born, born)
     assert_equal 0, age_in_years(born, Date.parse("Jan 2, 2005"))
     assert_equal 0, age_in_years(born, Date.parse("Dec 31, 2005"))
     assert_equal 1, age_in_years(born, Date.parse("Jan 1, 2006"))
   end

   If you are pointing out that asking for the age of someone who is not born yet (i.e. the today date is prior to the birth date) produces nonsensical output, then indeed it does.

   If defining age_in_years for that particular condition is important, one needs to decide what the proper outcome is (zero?, negative years?, exception?) and add the appropriate test cases.

   For myself, I should have stated that the precondition for age_in_years was that today >= born rather than leave it implicit in the tests.

   —Jim

4. nukeedit
   Lewis said about 20 hours later:
   

   Sorry, you guys are right, it’s not really a bug just undefined. The function totally works as written, it just when I ran it with my birthday, one of the tests failed.

   Maybe a test_lewis_birthday should be required on all date classes :)

   (or maybe not)

5. nukeedit
   Sean Smith said 6 days later:
   

   The paste is gone! That’s what I get for leaving readings for later….

6. nukeedit
   Christopher Jones said 3 months later:
   

   Anyone have the code from the paste. I thought I had found the answer to my problem but the paste is gone. Even archive.org does not have it.

   You can email me at the given address. Thanks.

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