Run unit test with Ruby 2.0 and minitest 5.5 without Gemfile - ruby

Question

I was learning Ruby by reading Programming Ruby and there is this example code:
require_relative 'count_frequency'
require_relative 'words_from_string'
require 'test/unit'
class TestWordsFromString < Test::Unit::TestCase
def test_empty_string
assert_equal([], words_from_string(''))
assert_equal [], words_from_string(' ')
end
def test_single_word
assert_equal ['cat'], words_from_string('cat')
assert_equal ['cat'], words_from_string(' cat ')
end
def test_many_words
assert_equal ['the', 'cat', 'sat', 'on', 'the', 'cat'], words_from_string('the cat sat on the mat')
end
def test_ignore_punctuation
assert_equal ['the', "cat's", 'mat'], words_from_string("the cat's mat")
end
end
When I tried to run it, an error occured:
MiniTest::Unit::TestCase is now Minitest::Test.
More detailed error message:
I'm using ruby 2.0.0p481 (2014-05-08 revision 45883) [universal.x86_64-darwin14] and minitest (5.5.0, 5.4.3, 5.3.5, 4.3.2). I did some search and found that since minitest5.0, MiniTest::Unit::TestCase has changed to Minitest::Test. But I cannot do anything since it's in the source file of the gem. Some suggests that require minitest 4.** in Gemfile, but i'm just running a few scripts. There is no need for Gemfile I suppose. And I certainly don't want to uninstalling minitest5.**. So is there a way I could run this script with minitest5.5 and ruby 2.0?

Answer 1

The tests should still run. I have the same set up and even though I get that error, the tests are executed.
→ ruby --verbose etl_test.rb
MiniTest::Unit::TestCase is now Minitest::Test. From etl_test.rb:4:in `<main>'
Run options: --seed 61653
# Running:
....
Finished in 0.001316s, 3039.5137 runs/s, 3039.5137 assertions/s.
4 runs, 4 assertions, 0 failures, 0 errors, 0 skips
classyhacker:~/dev/github/exercism/ruby/etl
→ rbenv versions
system
1.9.3-p448
2.0.0-p451
2.1.0
2.1.1
2.1.2
* 2.1.3 (set by RBENV_VERSION environment variable)
jruby-1.7.8
classyhacker:~/dev/github/exercism/ruby/etl
→ gem list | grep minitest
minitest (5.5.1, 5.4.3, 4.7.5)
My test looks like
require 'minitest/autorun'
require_relative 'etl'
class TransformTest < MiniTest::Unit::TestCase
def test_transform_one_value
old = { 1 => ['A'] }
expected = { 'a' => 1 }
assert_equal expected, ETL.transform(old)
end
require minitest/autorun is also the suggested way in rubydoc http://ruby-doc.org/stdlib-2.0.0/libdoc/minitest/rdoc/MiniTest.html