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なんか本に書いてあることが全然違うなー。本の内容は1.2なので仕方ないけど。
とりあえず、Scaffoldで生成されたテストを実行するとエラーになります。

% rake                                                         tenkoma@tenkoimac
(in /Users/tenkoma/NetBeansProjects/memopad)
/opt/local/bin/ruby -Ilib:test "/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.3/lib/rake/rake_test_loader.rb" "test/unit/memo_test.rb" 
Loaded suite /opt/local/lib/ruby/gems/1.8/gems/rake-0.8.3/lib/rake/rake_test_loader
Started
.
Finished in 0.023451 seconds.

1 tests, 1 assertions, 0 failures, 0 errors
/opt/local/bin/ruby -Ilib:test "/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.3/lib/rake/rake_test_loader.rb" "test/functional/memos_controller_test.rb" 
Loaded suite /opt/local/lib/ruby/gems/1.8/gems/rake-0.8.3/lib/rake/rake_test_loader
Started
F......
Finished in 0.131401 seconds.

  1) Failure:
test_should_create_memo(MemosControllerTest)
    [/opt/local/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/testing/core_ext/test/unit/assertions.rb:51:in `assert_difference'
     /opt/local/lib/ruby/gems/1.8/gems/actionpack-2.2.2/lib/action_view/renderable.rb:83:in `each_with_index'
     /opt/local/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/testing/core_ext/test/unit/assertions.rb:47:in `each'
     /opt/local/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/testing/core_ext/test/unit/assertions.rb:47:in `each_with_index'
     /opt/local/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/testing/core_ext/test/unit/assertions.rb:47:in `assert_difference'
     ./test/functional/memos_controller_test.rb:16:in `test_should_create_memo'
     /opt/local/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/testing/setup_and_teardown.rb:60:in `__send__'
     /opt/local/lib/ruby/gems/1.8/gems/activesupport-2.2.2/lib/active_support/testing/setup_and_teardown.rb:60:in `run']:
<Memo.count> was the expression that failed.
<3> expected but was
<2>.

7 tests, 9 assertions, 1 failures, 0 errors
/opt/local/bin/ruby -Ilib:test "/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.3/lib/rake/rake_test_loader.rb"  
Errors running test:functionals!

エラーになっているのは、test/functional/memos_controller_test.rbの16行目のassert_differenceの所みたいです。

  test "should create memo" do
    assert_difference('Memo.count') do
      post :create, :memo => { }
    end

    assert_redirected_to memo_path(assigns(:memo))
  end

ぐぐって、assert_differenceについて調べると、評価式の結果が変わることを検査するということのようです。つまり、まず、ブロックを実行する前にMemo.countの値を調べておいて、ブロックを実行したあとにまた評価して、値が変わればアサーションにパスすると。
で、なぜテストに失敗するのかというと、ここでは、「post :create...」でMemoを投稿していますが、バリデーションではじかれてるんですね。3日目の1時限目に追加したバリデーションは以下の通り。(app/models/memo.rb)

class Memo < ActiveRecord::Base
  validates_presence_of :text, :location
  validates_length_of :location, :within => 4..8
  validates_exclusion_of :location, :in => %w(school street)
end

なので、これに併せてテストを修正しなくてはいけません。

  test "should create memo" do
    assert_difference('Memo.count') do
      post :create, :memo => {:text => 'テストデータ#3', :location => 'テストテスト'}
    end

    assert_redirected_to memo_path(assigns(:memo))
  end