ruby-on-rails-3 - レールでこの包含検証を機能させることができません

Question

Rspecを使用してモデルで性別のテストを作成しようとしています-次のようになります:

it "should require a valid gender" do
  wrong_gender_student = @student_group.students.create!(@student_attr.merge(gender: "Zlorp"))
  wrong_gender_student.should_not be_valid
end

予想どおり、失敗します。

1) Student should require a valid gender
 Failure/Error: wrong_gender_student.should_not be_valid
   expected #<Student id: 2, name: "Example Student", gender: "Zlorp", created_at: "2013-05-28 16:25:53", updated_at: "2013-05-28 16:25:53", student_group_id: 1> not to be valid

ただし、コードを追加して通過させる場合:

class Student < ActiveRecord::Base
  attr_accessible :gender, :name

  belongs_to :student_group
  has_many   :subjects
  has_many   :characteristics

  VALID_GENDERS = %w(Male Female Transgender)

  validates :gender, inclusion: { :in => VALID_GENDERS,
                                :message => "%{value} is not a valid gender" }

end

それでも失敗し、検証テストは機能しているように見えますが、「Zlorp」に合格していません - 以下の性別は「Nil」です

  1) Student should require a valid gender
 Failure/Error: association_attr #this is a list of variables in spec_helper.rb
 ActiveRecord::RecordInvalid:
   Validation failed: Gender  is not a valid gender

編集:これはassociation_attrです:

def association_attr
  # User attritbutes 
  @user = Factory(:user)

  # Student_group
  @student_group = @user.student_groups.create!(@student_group_attr)
  # Student_group attributes
  @student_group_attr = { name: "4a" }

  # Student 
  @student = @student_group.students.create!(@student_attr)
  # Student attributes
  @student_attr = { gender: "Female", name: "Example Student" }

  # Subject
  @subject = @student.subjects.create!(@subject_attr)
  # Subject attributes
  @subject_attr = { name: "English", end_date: @date }
  @date = Date.today+180

  # Goal
  @goal = @subject.goals.create!(@goal_attr)
  # Goal attributes
  @goal_attr = { goal: "To unlearn the evil" }

  # Characteristic
  @characteristic = @student.characteristics.create!(@char_attr)
  # Characteristic attributes
  @char_attr = { characteristic: "Dyslexic" }

  # Age_group
  # For has_one associations use 'create_object'
  # http://stackoverflow.com/questions/7479083/ruby-on-rails-3-has-one-association-testing
  @age = @student_group.create_age!(@age_attr)
  # Age attributes
  @age_attr = { age: "older adults"}
end

どうしたの？