以前的随笔都是按照书上的例子写下来的，但是，这次在测试Model时，按照书上的例子代码怎么也走不通，所以就换个方式，这篇变成了提问。
按照书上的说法，在products_test.rb开始的时候，会根据定义的yml文件，加载测试数据到一个Hash里，这样，在test的时候我们就可以根据yml文件中用例的名字来访问一个product对象，例如：
def test_read_with_hashassert_kind_of Product, @productvc_book = @products["version_control_book"]assert_equal vc_book["id"], @product.idassert_equal vc_book["title"], @product.titleassert_equal vc_book["description"], @product.descriptionassert_equal vc_book["image_url"], @product.image_urlassert_equal vc_book["price"], @product.priceassert_equal vc_book["date_available"], @product.date_available_before_type_castend
但是，根据在运行测试的时候总是提示vc_book为Null的错误：
3) Error:
test_read_with_hash(ProductTest):NoMethodError: You have a nil object when you didn't expect it!You might have expected an instance of Array.The error occurred while evaluating nil.[] test/unit/product_test.rb:41:in `test_read_with_hash'
怎么回事呢？即使将product_test.rb里的内容全部替换成书中完整的代码也还是不行，是不是版本问题？
附product_test.rb全部代码：
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 assert_equal 29.95, @product.price assert_equal "2005-01-26 00:00:00", @product.date_available_before_type_cast end def test_update assert_equal 29.95, @product.price @product.price = 99.99 assert @product.save, @product.errors.full_messages.join("; ") @product.reload assert_equal 99.99, @product.price end #~ def test_destroy #~ @product.destroy #~ assert_raise(ActiveRecord::RecordNotFound) { Product.find(@product.id) } #~ end def test_validate assert_equal 29.95, @product.price @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 endend
青春在我的心中是苦涩的又是甘甜的，是精致的又是粗糙的，
