active-record-validations.md

Active Record Validations and Model Specs

Validations - Active Record statements that are added to the model class

• Run each time you create or update an instance
• Ensure the data that is getting passed in is what we are expecting

Setup

$ rails new validations -d postgresql -T $ cd validations $ rails db:create

Installed RSpec gem: $ bundle add rspec-rails

Generated a spec folder to hold our RSpec tests $ rails generate rspec:install

Generate a Model $ rails g model Animal name:string amount:integer

I want to check that Active Record will reject an instance that does not provide data on a specific column.

spec/models/animal_spec.rb

require 'rails_helper'

RSpec.describe Animal, type: :model do
  it "is valid with valid attributes" do
    animal = Animal.create(name:'Hazel', amount:1)
    expect(animal).to be_valid
  end

  it "is not valid without a name" do
    animal = Animal.create(amount:2)
    expect(animal.errors[:name]).to_not be_empty
  end
end

Good Fail!

Update model to have validations:

/app/models/animal.rb

class Animal < ApplicationRecord
  validates :name, presence: true
end

Make sure the new instance has an amount

spec/models/animal_spec.rb

 it "is not valid without an amount" do
    animal = Animal.create(name: "Hazel")
    expect(animal.errors[:amount]).to_not be_empty
  end

Good fail!

Update model to have validations:

/app/models/animal.rb

class Animal < ApplicationRecord
  validates :name, :amount, presence: true
end

Use the length property to make sure name is within a certain range of characters

spec/models/animal_spec.rb

it "is not valid if name is outside 3-20" do
  animal = Animal.create(name: 'Z', amount:1)
  expect(animal.errors[:name]).to_not be_empty
end

Good Fail!

Update model with length validation

class Animal < ApplicationRecord
  validates :name, :amount, presence: true
  validates :name, length: { in: 3..20 }
end

Final Result:

spec/models/animal_spec.rb

require 'rails_helper'

RSpec.describe Animal, type: :model do
  it "is valid with valid attributes" do
    animal = Animal.create(name:'Hazel', amount:1)
    expect(animal).to be_valid
  end

  it "is not valid without a name" do
    animal = Animal.create(amount:2)
    expect(animal.errors[:name]).to_not be_empty
  end

  it "is not valid without an amount" do
    animal = Animal.create(name: "Hazel")
    expect(animal.errors[:amount]).to_not be_empty
  end

  it "is not valid if name is outside 3-20" do
    animal = Animal.create(name: 'Z', amount:1)
    expect(animal.errors[:name]).to_not be_empty
  end
end

models/animal.rb

class Animal < ApplicationRecord
    validates :name, :amount, presence: true
    validates :name, length: { in: 3..20 }
end