Test sequence discovering how microseconds can cause your tests to fail while reporting that all looks equal

damn_you_usec.rb

# Givens: Rails 3.0.7, Ruby 1.9.2, with RSpec2 (2.6.4) and FactoryGirl (1.3.3)

# original test ...
require 'spec_helper'

describe Item do
  context 'a trivial example' do
    before do
      @item = Factory.create(:item)
    end

    it 'updates created_at without issue' do
      new_time = 1.day.ago
      @item.created_at = new_time
      @item.created_at.should == new_time
    end
  end
end

# This fails with the perplexing error of ...
# Failure/Error: @item.created_at.should == new_time
#   expected: Sat, 16 Jul 2011 23:14:08 UTC +00:00
#        got: Sat, 16 Jul 2011 23:14:08 UTC +00:00 (using ==)
# "WTF?" I thought, "Those are the same!"

# Next, I checked if #to_s'ing each did anything
require 'spec_helper'

describe Item do
  context 'a trivial example' do
    before do
      @item = Factory.create(:item)
    end

    it 'updates created_at without issue' do
      new_time = 1.day.ago
      @item.created_at = new_time
      @item.created_at.to_s.should == new_time.to_s
    end
  end
end

# This passes. I next started to look into what types of objects were being returned.
# Both were ActiveSupport::TimeWithZone, dead end.
# Next, I tried #to_date'ing each, which got a passing test. #to_datetime'ing each caused a failure.
# So it is something with the time component.

# After a little digging, I thought to check microseconds:
require 'spec_helper'

describe Item do
  context 'a trivial example' do
    before do
      @item = Factory.create(:item)
    end

    it 'TEMP: helps me examine the two dates' do
      new_time = 1.day.ago
      @item.created_at = new_time
      @item.created_at.usec.should == new_time.usec
    end
  end
end

# Fail! Yay! Full error reported by RSpec is:
# Failure/Error: @disease_state.created_at.usec.should == new_time.usec
#       expected: 432826
#            got: 0 (using ==)

# So the microseconds part is being populated when using 1.day.ago
# Solution? Get rid of the microseconds!
require 'spec_helper'

describe Item do
  context 'a trivial example' do
    before do
      @item = Factory.create(:item)
    end

    it 'updates created_at without issue' do
      new_time = Time.zone.local(2011, 7, 16, 12, 0, 0)
      @item.created_at = new_time
      @item.created_at.should == new_time
    end
  end
end

# All green. Don't let the microseconds issue bite you in the ass in your test assertions.