ActiveRecord モデルテストの例

20111125000000_crate_foos.rb

class CreateFoos < ActiveRecord::Migration
  def change
    create_table :foos do |t|
      t.string :bar, null: false

      t.timestamps
    end
    add_index :foos, :bar, unique: true
  end
end

20111125000000_create_items.rb

class CreateItems < ActiveRecord::Migration
  def change
    create_table :items do |t|
      t.integer :vendor_id, null: false
      t.string :title, null: false
      t.string :description
      t.decimal :price, precision: 10, scale: 2, null: false

      t.timestamps
    end
    execute %{
      ALTER TABLE items ADD CONSTRAINT title_check CHECK (title <> '');
      ALTER TABLE items ADD CONSTRAINT price_check CHECK (price >= 0);
      ALTER TABLE items ADD FOREIGN KEY (vendor_id) REFERENCES vendors (id);
    }
  end
end

foo.rb

class Foo < ActiveRecord::Base
  validates :bar, presence: true, uniqueness: true
end

item.rb

class Item < ActiveRecord::Base
  belongs_to :vendor

  validates :title, presence: true
  validates :price, numericality: { :greater_than_or_equal_to => 0 }
end

item_test.rb

require 'test_helper'

class ItemTest < ActiveSupport::TestCase
  test 'an item with boundary value attributes is valid' do
    assert build(:item_with_boundary_value_attributes).valid?
  end

  test 'an item with empty title is invalid' do
    item = build(:item_with_empty_title)
    assert item.invalid?
    assert item.errors[:title].any?
  end

  test 'an item with blank title is invalid' do
    item = build(:item_with_blank_title)
    assert item.invalid?
    assert item.errors[:title].any?
  end

  test 'an item with empty price is invalid' do
    item = build(:item_with_empty_price)
    assert item.invalid?
    assert item.errors[:price].any?
  end

  test 'an item with negative price is invalid' do
    item = build(:item_with_negative_price)
    assert item.invalid?
    assert item.errors[:price].any?
  end

  test 'db allows saving an item with boundary value attributes' do
    assert build(:item_with_boundary_value_attributes).save
  end

  test 'db can catch null title' do
    assert_statement_invalid do
      build(:item_with_empty_title).save!(validate: false)
    end
  end

  test 'db can catch blank title' do
    assert_statement_invalid do
      build(:item_with_blank_title).save!(validate: false)
    end
  end

  test 'db can catch null price' do
    assert_statement_invalid do
      build(:item_with_empty_price).save!(validate: false)
    end
  end

  test 'db can catch negative price' do
    assert_statement_invalid do
      build(:item_with_negative_price).save!(validate: false)
    end
  end

  test 'db can catch null vendor_id' do
    assert_statement_invalid do
      build(:item, vendor_id: nil).save!(validate: false)
    end
  end

  test 'db can catch an item with invalid reference' do
    assert_invalid_foreign_key do
      build(:item, vendor_id: 99999999).save!(validate: false)
    end
  end
end

items.rb

FactoryGirl.define do
  factory :item, aliases: [:item_with_boundary_value_attributes]  do
    vendor
    title "Q"
    description "Using this item, you will be taller."
    price '0.00'

    factory :item_with_empty_title do
      title nil
    end

    factory :item_with_blank_title do
      title ''
    end

    factory :item_with_empty_price do
      price nil
    end

    factory :item_with_negative_price do
      price '-128.75'
    end
  end
end

ActiveRecord モデルテストの書き方ガイドライン に embed したもの