使用 RSpec 测试模型时出现错误“nil:NilClass 的未定义方法 `<'”。

Question

我正在学习 RSpec 并测试以下场景：

require 'rails_helper'

RSpec.describe Student, type: :model do
  before(:each) do
    Student.delete_all
  end

  it "roll number can't be less than 0 or more than 80" do
    s = Student.create(:name => "sanjay" , :lastname => "test" , :roll => 0)
    s1 = Student.create(:name => "sanjay" , :lastname => "test" , :roll => 81)
    expect(s).not_to be_valid
    expect(s1).not_to be_valid
  end
end

以下是学生模型定义：

class Student < ActiveRecord::Base
  validates_presence_of :name
  validates_uniqueness_of :roll
  validate :number_of_valid_students
  def number_of_valid_students
    if (self.roll < 1)  or (self.roll > 80)
      self.errors.add(:rollnumber , "Can't be less than 0 or greater than 80")
    end
  end
end

运行命令rake spec:models 后出现以下错误：

 Failure/Error: expect(student).not_to be_valid
 NoMethodError:
   undefined method `<' for nil:NilClass

请帮忙。 谢谢。

Answer 1

您不需要添加自定义验证。考虑使用 ActiveRecord 提供的numericality validation：

class Student < ActiveRecord::Base
  validates :name, presence: true
  validates :roll, uniqueness: true
  validates :roll, numericality: { greater_than: 1, less_than: 80 }
end

也可以这样写你的测试：

let(:student1) { Student.create(name: "sanjay", lastname: "test", roll: 0) }
let(:student2) { Student.create(name: "sanjay", lastname: "test", roll: 81) }

it "roll number can't be less than 0 or more than 80" do
  expect(student1).not_to be_valid
  expect(student2).not_to be_valid
end

查看Better Specs 了解 RSpec 最佳实践。