Agile Web Development with Rails MODEL测试框架 test_* (ProductTest) 出现很多错误

可能很多朋友在参照第一版<Pragmatic Bookshelf,Agile Web Development with Rails >写测试的时候碰到了大量的错误，这些不是因为我们的代码抄错了，而是由于我们不是很了解这个测试框架的一些配置参数。
我的环境


Ubuntu 7.10


Eclipse Version: 3.3.0 + RadRails


Mysql 5.x


Ruby 1.8.6


Rails 1.2.4

这是我的代码


require File.dirname(__FILE__) + '/../test_helper'




class ProductTest < Test::Unit::TestCase


fixtures :products




def setup


@product = Product.find(1)


end


# Replace this with your real tests.


def test_truth


assert_kind_of Product, @product


end




def test_create


assert_kind_of Product, @product


assert_equal 1, @product.id


assert_equal "Pragmatic Version Control", @product.title


assert_equal "How to use version control", @product.description


assert_equal "http://.../sk_svn_small.jpg", @product.image_url


a = @product.price.to_s


assert_equal "29.95" , a


assert_equal "2005-01-26 00:00:00", @product.date_available_before_type_cast


end




def test_update


assert_equal "29.95", @product.price.to_s


@product.price = 99.99


assert @product.save, @product.errors.full_messages.join("; ")


@product.reload


assert_equal "99.99" ,@product.price.to_s


end




def test_destroy


@product.destroy


assert_raise(ActiveRecord::RecordNotFound){ Product.find(@product.id) }


end




def test_validate


assert_equal "29.95", @product.price.to_s


@product.price = 0.00


assert !@product.save


assert_equal 1, @product.errors.count


assert_equal "should be positive", @product.errors.on(:price)


end




def test_read_with_hash


assert_kind_of Product, @product


vc_book = @products["version_control_book"]


assert_equal vc_book["id"], @product.id


assert_equal vc_book["title"], @product.title


assert_equal vc_book["description"], @product.description


assert_equal vc_book["image_url"], @product.image_url


assert_equal vc_book["price"], @product.price


assert_equal vc_book["date_available"], @product.date_available_before_type_cast


end




def test_read_with_fixture_variable


assert_kind_of Product, @product


assert_equal @version_control_book.id, @product.id


assert_equal @version_control_book.title, @product.title


assert_equal @version_control_book.description, @product.description


assert_equal @version_control_book.image_url, @product.image_url


assert_equal @version_control_book.price, @product.price


assert_equal @version_control_book.date_available, @product.date_available


end






end



如果直接运行可能会出现一些错误：


NoMethodError with test_read_with_hash




Failure:


test_create(ProductTest) [test/unit/product_test.rb:16]:


<29> expected but was


<#<BigDecimal:4aad7b0,'0.2995E2',8(8)>>.




Error:


test_update(ProductTest):


ActiveRecord::RecordNotFound: Couldn't find Product with ID=1



需要我们修改参数了
depot/test/test_helper.rb
set


self.use_transactional_fixtures = false #原本希望通过事务回滚来还原数据


self.use_instantiated_fixtures = true

详细解释：
在使用Mysql的时候Talbe的默认storage engine 是MyISAM，而Rails的测试框架是默认是希望通过事务回滚机制来还原数据。但是MyISAM是不支持回滚的，所以无法还原数据，导致假象上的生命周期讲解有问题。所以也可以通过switching from MyISAM to InnoDB 来达到同样的效果。
这样就可以了。不过不能怪写书的，毕竟在用例子作为讲义时难免由于直接讲配置不容易理解而导致错误的。