NameError: undefined local variable or method `logger'

When I run 'script/server' everything works fine, but when I run my unit tests (rake test:units), I get the error below, and am not sure how to solve this.

Error

NameError: undefined local variable or method `logger' for #<GiveawayEligibleMemberTest:0x10477dff8>
    /Users/kamilski81/Sites/pe/vitality_mall/vendor/rails/actionpack/lib/action_controller/test_process.rb:471:in `method_missing'
    /Users/kamilski81/Sites/pe/vitality_mall/lib/update_giveaway_eligible_members.rb:17:in `is_valid_checksum?'
    /Users/kamilski81/Sites/pe/vitality_mall/test/unit/giveaway_eligible_member_test.rb:26:in `test_that_checksum_is_valid'
    /Users/kamilski81/Sites/pe/vitality_mall/vendor/rails/activesupport/lib/active_support/testing/setup_and_teardown.rb:60:in `__send__'
    /Users/kamilski81/Sites/pe/vitality_mall/vendor/rails/activesupport/lib/active_support/testing/setup_and_teardown.rb:60:in `run'

I tried putting:

class Test::Unit::TestCase
  RAILS_DEFAULT_LOGGER = Logger.new(STDOUT)
  RAILS_DEFAULT_LOGGER.level = Logger::WARN

  logger = Logger.new(STDOUT)
  logger.level = Logger::WARN
end

Here is the code that is using my logger:

def is_valid_checksum?(csv_arr)
  expected_row_count = csv_arr[0][3].to_i
  logger.debug "Expected record count: #{expected_row_count}"
  actual_row_count = csv_arr.nitems - 1
  logger.debug "Actual record count: #{actual_row_count}"
  checksum_valid = false
  if expected_row_count == actual_row_count
    logger.debug "Checksum is valid"
    checksum_valid = true
  end

  return checksum_valid
end

But this still does not solve the error