Rails 测试 has_many 关联失败

Question

我有 2 个型号。一个用户和一个任务。这是它们的代码：

class User < ActiveRecord::Base
  has_many :tasks
  has_many :assigned_tasks, :class_name => 'Task', :foreign_key => 'assigned_user_id'
end

class Task < ActiveRecord::Base
  belongs_to :user
  belongs_to :assigned_user, :class_name => 'User', :foreign_key => 'assigned_user_id'
end

该架构非常明显，但为了保持一致性，它看起来是这样的：

ActiveRecord::Schema.define(:version => 20110925050945) do
  create_table "tasks", :force => true do |t|
    t.string   "name"
    t.integer  "user_id"
    t.integer  "assigned_user_id"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  create_table "users", :force => true do |t|
    t.string   "name"
    t.datetime "created_at"
    t.datetime "updated_at"
  end
end

我为分配的任务关系添加了一个测试用例。它看起来像这样：

class UserTest < ActiveSupport::TestCase
  test "assigned tasks" do
    u1 = User.create(:name => 'john')
    u2 = User.create(:name => 'dave')

    assert_empty u2.assigned_tasks # LOOK AT ME

    task = u1.tasks.create(:name => 'some task', :assigned_user_id => u2.id)

    assert_equal 1, u2.assigned_tasks.size
  end
end

现在，这个测试用例失败了。最后一个断言失败了。如果我删除之前的断言（标记为“LOOK AT ME”），则该测试会顺利通过。如果我将此行更改为 assert u2.assigned_tasks，它也会顺利通过。这意味着当且仅当针对 u2.assigned_tasks 调用 empty? 时，它才会出现中断。如果该断言通过，则下一个断言就会失败。失败如下：

UserTest:
     FAIL assigned tasks (0.12s) 
          <1> expected but was
<0>.
          test/unit/user_test.rb:12:in `block in <class:UserTest>'

因此，一旦在原始 u2.assigned_tasks 数组上调用 empty? ，任务实际上并未添加/与其分配的用户关联。然而，这在控制台中似乎工作正常。

如果我在这里完全忽略了一些简单的事情，我很抱歉，但我真的无法理解这一点。任何方向正确的观点都会非常有帮助。谢谢

PS：带有普通应用程序的 Rails 3.1

Answer 1

您需要重新加载 signed_tasks 或 u2。

# This line causes assigned_tasks to be loaded and cached on u2.  Not the calling
# of empty?, but rather the loading of the association.
assert_empty u2.assigned_tasks

# but then you actually make the task here
task = u1.tasks.create(:name => 'some task', :assigned_user_id => u2.id)

# so when this assertion happens, u2 already has an empty set of tasks cached, 
# and fails
assert_equal 1, u2.assigned_tasks.size

# however either of these should pass
assert_equal 1, u2.assigned_tasks(true).size
assert_equal 1, u2.reload.assigned_tasks.size

inverse_of 选项用于改进内存中关联行为，并且还可能解决您的问题（无需重新加载）。请在此处了解相关内容。它看起来像这样（但我再次不确定它在这种情况下是否有效）：

# on User
has_many :assigned_tasks, ..., :inverse_of => :assigned_user

# on Task
belongs_to :assigned_user, ..., :inverse_of => :assigned_tasks

# in your test you might have to change the task creation to:
u1.tasks.create(:name => 'some task', :assigned_user => u2)