```After looking through some of the other solutions to this quiz, I
decided to adapt some of the good ideas I found to improve my own
solution. Using Test::Unit to for testing was the first modification
I wanted to make. I have never used Test::Unit up to now. I thought
it was high time for me to do so.

Since changing over to Test::Unit doesn't really change my solution,
I didn't plan to repost it after making the change. I changed my mind
because I ran into something with Test::Unit that really surprised
me. First, the modified code and then some more discussion.

<code>
require 'test/unit'

class DayRange

DAY_DIGITS = {
'mon' => 1,
'tue' => 2,
'wed' => 3,
'thu' => 4,
'fri' => 5,
'sat' => 6,
'sun' => 7,
'monday' => 1,
'tuesday' => 2,
'wednesday' => 3,
'thursday' => 4,
'friday' => 5,
'saturday' => 6,
'sunday' => 7,
'1' => 1,
'2' => 2,
'3' => 3,
'4' => 4,
'5' => 5,
'6' => 6,
'7' => 7
}

SHORT_NAMES = %w[_ Mon Tue Wed Thu Fri Sat Sun].freeze

LONG_NAMES = %w[_ Monday Tuesday Wednesday Thursday
Friday Saturday Sunday].freeze

# Return day range as nicely formatted string.
# If @long is true, day names appear in long form; otherwise, they
# appear in short form.
def to_s
names = @long ? LONG_NAMES : SHORT_NAMES
result = []
@days.each do |d|
case d
when Integer
result << names[d]
when Range
result << names[d.first] + "-" + names[d.last]
end
end
result.join(", ")
end

# Return day range as array of integers.
def to_a
result = @days.collect do |d|
case d
when Integer then d
when Range then d.to_a
end
end
result.flatten
end

def initialize(*args)
@days = []
@long = false
@args = args
@args.each do |arg|
case arg
when Integer
bad_arg if arg < 1 || arg > 7
@days << arg
when /^(.+)-(.+)\$/
begin
d1 = DAY_DIGITS[\$1.downcase]
d2 = DAY_DIGITS[\$2.downcase]
bad_arg unless d1 && d2 && d1 <= d2
d1.upto(d2) {|d| @days << d}
rescue StandardError
end
else
d = DAY_DIGITS[arg.downcase]
@days << d
end
end
@days.uniq!
@days.sort!
normalize
end

# Use this to change printing behavior from short day names to long day
# names or vice-versa.
attr_accessor :long

private

# Convert @days from an array of digits to normal form where runs of
# three or more consecutive digits appear as ranges.
def normalize
runs = []
first = 0
for k in 1... / days.size
unless @days[k] == @days[k - 1].succ
runs << [first, k - 1] if k - first > 2
first = k
end
end
runs << [first, k] if k - first > 1
runs.reverse_each do |r|
@days[r..r] = @days[r]..@days[r]
end
end

raise(ArgumentError,
"Can't create a DayRange from #{@args.inspect}")
end

end

class TestDayRange < Test::Unit::TestCase

# All these produce @days == [1..7].
ONE_RANGE = [
%w[mon tue wed thu fri sat sun],
%w[monDay tuesday Wednesday Thursday friDAY saturday SUNDAY],
%w[mon-fri sat-sun],
%w[4-7 1-3],
(1..7).to_a.reverse,
[4, 7, 6, 5, 4, 1, 2, 1, 2, 3, 3, 7, 6, 5],
]

# Both these produce @days == [1..3, 5..7].
TWO_RANGES = [
%w[mon-mon tue-tue wed-wed fri-sun],
[1, 2, 'mon-wed', 'friday', 6, 7]
]

INVALID_ARGS = [
[1, 2, 'foo'],
%w[foo-bar],
%w[sat-mon],
(0..7).to_a.reverse,
(1..8).to_a
]

@@one_range = []
@@two_ranges = []

def test_args_helper(args, expected)
obj = nil
assert_nothing_raised(ArgumentError) {obj = DayRange.new(*args)}
assert_equal(expected, obj.instance_variable_get(:@days))
obj
end

def test_valid_args
ONE_RANGE.each do |args|
@@one_range << test_args_helper(args, [1..7])
end
TWO_RANGES.each do |args|
@@two_ranges << test_args_helper(args, [1..3, 5..7])
end
puts "test_valid_args -- #{@@one_range.size}, #
{@@two_ranges.size}"
end

INVALID_ARGS.each do |args|
assert_raise(ArgumentError) {DayRange.new(*args)}
end
end

def test_to_s
puts "test_to_s -- #{@@one_range.size}, #{@@two_ranges.size}"
@@one_range.each do |obj|
assert_equal('Mon-Sun', obj.to_s)
end
@@two_ranges.each do |obj|
assert_equal('Mon-Wed, Fri-Sun', obj.to_s)
end
end

def test_to_a
puts "test_to_a -- #{@@one_range.size}, #{@@two_ranges.size}"
@@one_range.each do |obj|
assert_equal((1..7).to_a, obj.to_a)
end
@@two_ranges.each do |obj|
assert_equal([1, 2, 3, 5, 6, 7], obj.to_a)
end
end

end
</code>

<result>
Started
.test_to_a -- 0, 0
.test_to_s -- 0, 0
.test_valid_args -- 6, 2
.
Finished in 0.010845 seconds.

4 tests, 21 assertions, 0 failures, 0 errors
</result>

None of the assertions in test_to_s and test_to_a execute. This is
because @@one_range and @@two_ranges are both empty when these tests
are run. My plan of creating the test objects in test_valid_args and
reusing them in test_to_s and test_to_a fails. This happens because
the tests are run, not in the order in which they appear in the
source code, but in the sort order of their names. How strange!

The fix is obvious and I have already applied it: rename
test_valid_args to test_args so it runs first.

I've posted this because it took me longer to trace down this problem
than it took me to write the TestDayRange class. I will consider it
worth the effort if the posting helps one other person to avoid this
trap. On the other hand, if I'm guilty of belaboring a well-known
"feature" of Test::Unit, I apologize.

Regards, Morton

```