Testing Inventory

Objective: Use TDD in Rails to create an inventory management application. Your goals are:

• write code to pass some existing tests
• write and pass tests for other features

Getting Started

1. Fork this repo, and clone it onto your local machine.
2. Run bundle update and bundle install to update and install gems.
3. Run rails db:create db:migrate to create and migrate the database.
4. Start your Rails server.
5. The primary gem you'll use for testing this app is rspec-rails. You may also use factory_girl_rails to set up and tear down test data, ffaker to create realistic fake data, and shoulda-matchers for extra matchers. Examine your Gemfile to make sure these gems are included.
6. Run rspec in the Terminal. You should see 0 examples, 0 failures.
7. Create a new my-items-intro branch to start working on, and switch to it.

What's Already Been Done

• Gems rspec-rails, factory_girl_rails, shoulda-matchers, and ffaker (and a few others) are installed in the Gemfile for the development and test groups.
• Terminal command rails generate rspec:install has been run, creating the .rspec file and the spec directory and its contents.

Intro: Items TDD

Goal: Set up items controller test files.

• Use Rails to generate an rspec controller test file for the items controller: rails g rspec:controller items. Read the Terminal output, and open the new file that was created.

• This spec file references the ItemsController, which isn't set up yet. Run rspec now to see the error uninitialized constant ItemsController (NameError).

• Use Rails to generate an items controller. Read the Terminal output - note that Rails attempted to create the spec file again because rspec-rails is included in the project.

• Run rspec to confirm your tests are no longer throwing errors.

Goal: Set up item model test files.

• Use Rails to generate rspec model test files for the items model: rails g rspec:model item. Note that this command creates two new files. One is a factory, and the other is the Item model spec.

• Run rspec to see the error uninitialized constant Item (NameError).

• Use Rails to generate an item model. Items will have three attributes: color, size, and status. Read the Terminal output to see which files are created. Choose y to overwrite the factory file if there is a conflict.

• Run rspec to confirm the tests are working. If they are, you will see "pending" tests. You may see an error - pause to debug it!

Goal: Test the items#show controller action.

• Add a RESTful route to config/routes.rb that will trigger the items controller's show action. To follow Rails conventions, make it a named route with the name or "prefix" item. Run rails routes.

  click to see route syntax

  `get '/items/:id' => 'items#show', as: :item`

• In your items controller spec file, add this section to test the items#show controller action:

  # spec/controllers/items_controller_spec.rb
  RSpec.describe ItemsController, type: :controller do
    describe "#show" do
      it "renders the :show view" do
        item = Item.create({size:'s', color:'blue', status:'unsold'})
        get :show, id: item.id
        expect(response).to render_template(:show)
      end
    end
  end

• Discuss with a partner what each line in the test above does. Refer to the rspec-rails controller spec docs.

  click for solution

    # spec/controllers/items_controller_spec.rb
  
    # set up controller tests for the ItemsController
    RSpec.describe ItemsController, type: :controller do  
      # set up tests for the show action, specifically
      describe "#show" do  
        # say how to test one goal of the show action
        it "renders the :show view" do  
          item = Item.create({size:'s', color:'blue', status:'unsold'}) # create test item
          get :show, id: item.id  # make a get request to /items/:id
          expect(response).to render_template(:show)  # test that response renders show view
        end
      end
    end
  

• This test will require a show method in the items controller, and a show view for items. Add an empty show method to the items controller, and create an app/views/items/show.html.erb file if you don't have one yet.

• Run rspec spec/controllers and verify that your test passes.

• The show method should look up the item to display and assign an @item instance variable to be used in the view. Add a second test inside the describe #show block:

  it "assigns @item" do
    item = Item.create({size:'s', color:'blue', status:'unsold'})
    get :show, id: item.id  
    expect(assigns(:item)).to eq(item)
  end

• This isn't looking very DRY! Use the rspec-rails let helper method to assign the item at the beginning of the describe #show block:

  describe "#show" do
    let(:item) { Item.create({size:'s', color:'blue', status:'unsold'}) }
  
    it "renders the :show view" do
      get :show, id: item.id
      expect(response).to render_template(:show)
    end
  
    it "assigns @item" do
      get :show, id: item.id
      expect(assigns(:item)).to eq(item)
    end
  end

• To DRY up the tests further, use the rspec-rails before(:each) hook (method) to make a get request before each of the #show tests are run:

  describe "#show" do
    let(:item) { Item.create({size:'s', color:'blue', status:'unsold'}) }
  
    before(:each) do # same as `before do`
      get :show, id: item.id  
    end
  
    it "renders the :show view" do
      expect(response).to render_template(:show)
    end
  
    it "assigns @item" do
      expect(assigns(:item)).to eq(item)
    end
  end

• Run rspec spec/controllers, and write code to pass your tests.

Goal: Test the items#create controller action.

• Make the route in config/routes.rb that will route to the items#create action. Also make a route for the items#new action, since that's the action that will eventually serve a form and lead to the create route.

  click to see routes after this step

  ```ruby get '/items/new' => 'items#new', as: :new_item post '/items' => 'items#create' get '/items/:id' => 'items#show', as: :item ```

• Create skeleton (empty) methods in the items controller for the new and create actions.

• Make a new block in the items controller spec file (spec/controllers/items_controller_spec.rb) to describe the #create action.

• For this action, you'll test two different contexts: successful creates and validation failures. Add two context blocks inside the describe #create block.

  click to see what the `describe #create` block should look like now

  ```ruby # spec/controllers/items_controller_spec.rb # after the `describe #show block` describe "#create" do context "success" do end

  context "failed validations" do end end

  </details>
  
  

• Inside the "success" context, use let to set up a hash of valid item data. Then use before(:each) to make a post request to the create action with item data item_hash:

  context "success" do
    let(:item_hash) { { size: "XL", color: "heather", status: "sold" } }
    before(:each) do
      post :create, item: item_hash
    end
  end

• If the create is successful, the create action should redirect to the show page for the new item (redirects have an HTTP status of 302). Add the following test after the before(:each) block ends:

  it "redirects to 'item_path'" do
    expect(response.status).to be(302)
    expect(response.location).to match(/\/items\/\d+/)
  end

• The create method should add the new item to the database. Add another test to the success context that checks whether the number of items in the database increases when you give the create controller action the valid data.

  • Hint: Compare the Item.count before and after the request is made to create the new item.
  • Hint: Use rspec-rails equality matchers to check whether expected and actual values are the same.
  click for solution

  context "success" do
    let(:item_hash) { { size: "XL", color: "heather", status: "sold" } }
    let(:items_count) { Item.count }
  
    before(:each) do
      post :create, item: item_hash
    end
  
    # ...
  
    it "adds an item to the database" do
      expect(Item.count).to eq(items_count + 1)
    end
  end

• Your item model will eventually require that each item have a status. One way the create method could fail is to if someone tried to create an item with a nil status. Inside the "failed validations" context block, use let to set up an item data hash with a nil status.

• Also in the failed validations context, use before(:each) (or just before) to make a post request to the create action with your invalid item hash as data.

• If the item fails validations, the controller should redirect back to the form (on the new item path). Inside the "failed validations" context, add a test to check that it "redirects to 'new_item_path'" with a response of 302.

  click to see what the failed validations context should look like after the last 3 steps

  context "failed validations" do
    # set up item data without a status to cause validation failure
    let(:item_hash) { { size: "S", color: "sage", status: nil } }
  
    before do
      post :create, item: item_hash
    end
  
    it "redirects to 'new_item_path'" do
      expect(response.status).to be(302)
      expect(response).to redirect_to(new_item_path)
    end
  end

• If the item fails validations, the controller should add an error message to the flash hash. Add the following test:

  context "failed validations" do
    # ...
    it "adds a flash error message" do
      expect(flash[:error]).to be_present
    end
  end

Goal: Pass the controller tests!

• Run rspec spec/controllers, and fill in the show and create actions pass your tests. (You'll need to add a validation to the item model to ensure the status is present.)

Goal: More realistic test data.

• Take a closer look at the item factory file that Rails generated for you when you generated the model test: spec/factories/items.rb. Factory Girl is a gem that will set up and tear down instances of test data for your app. The current code sets up a factory to create and destroy item instances. It should look like this:

  # spec/factories/items.rb
  FactoryGirl.define do
    factory :item do
      color "MyString"
      size "MyString"
      status "MyString"
    end
  end

• Every time you use the factory above to create an item, you'll get an item with color, size, and status all equal to "MyString". Replace these values with different ones to change the items Factory Girl will create; for example:

  # spec/factories/items.rb
  FactoryGirl.define do
    factory :item do
      color "cerulean"
      size "M"
      status "sold"
    end
  end

• It can be helpful to test with data that is more realistic. Sometimes people use randomized data as well. The benefit is you might find edge cases in random data that you forgot initially. However, be extremely careful with randomized data, as this can introduce hard to track-down intermittent test failures.

• Use Factory Girl's "lazy attributes" and the Ruby array method sample to make the factory randomly assign either "sold" or "unsold" as the status of each item it creates.

  click for solution

  `status { ["sold", "unsold"].sample }`

• Use Factory Girl's lazy attributes and FFaker's Color module to make the factory assign a random color to each item.

  click for solution

  `color { FFaker::Color.name }`

Feel free to check your work against the solution-items-intro branch.

Part 1: Products

A product represents a kind of item sold by this app. Each of this app's products will store a name, a description, a category, a sku number (which may contain numbers and letters), and wholesale and retail prices. Both prices will be decimals, because Ruby's BigDecimal is more precise than a float!

1. Commit your work on your branch.
2. Check out the products-start branch.
3. Create and switch to a new my-work branch.

Reference the solution-products branch for guidance if you get stuck during this part of the lab.

Goal: Pass products controller tests.

• The failing specs are for a ProductsController. Implement the functionality for the ProductsController to pass the tests. Some tips:
  • Read the errors carefully. They will guide you as to what to do next.
  • Once you've gotten past the initial setup errors, and you have failing specs printing out in the Terminal, it may help to only run specific specs by name using rspec spec -e '#index'
• You DON'T need to implement fully-functioning views.
• To pass some of these tests, you'll have to add model validations to check that fields are present.
• Remember to use strong parameters in your controller.

Goal: Write tests for the product model.

• Once you have all the specs passing for the ProductsController, it's time to implement unit tests for a product model.

• Generate an rspec model test for the product model by running rails g rspec:model product. Read the log messages carefully and find the file(s) Rails expects you to use for testing. One of these files is spec/factories/products.rb. Do not overwrite this file! You'll use the factory in this file, with the gems Factory Girl and FFaker, to create data for testing.

• The other new file generated for your model tests is in spec/models. In this file, write tests for a product model instance method called margin. The #margin method should calculate and return the retail margin of the product instance. The retail margin is the retail price minus the wholesale price, divided by the retail price and expressed as a percentage.

  • What product to test with?

    You can use Factory Girl to `create` a sample product in the test code. (See the controller code for an example.) Also calculate the product's profit margin (by hand) so you know what you expect the `margin` method to return.

• Write a test to ensure that the #margin method returns a BigDecimal value.

• Write a test to endure that the #margin method returns a correct value for some example product.

• Run rspec spec/models, and read the output carefully. Fix any errors that are preventing your tests from running.

• Once you have your model tests running, write code to pass them!

Part 2: Nested Items

Now, you'll practice TDD more independently.

A product represents a type of product the site sells. (You can think of products as tshirts, for example.) The site allows customization of the the color and size of products, and it would be good to know the status of each particular item in the warehouse (sold/unsold). For this reason, products should have many items. Use TDD to guide your implementation of CRUD for items. That means write tests first.

Your items should be set up to have a minimum of three attributes: size, color, and status. The status will usually be "sold" or "unsold".

Note: Items routes should be nested under products routes. See the Rails docs for nested resources.

Reference the solution-nested-items branch for guidance if you get stuck during this part of the lab.

Goal: Set up factory for the item model.

• Generate test and factory files for the item model, if you don't have them yet. Generate the item model, if you don't have one yet.

• Take advantage of the factory_girl_rails and ffaker gems to define an item factory to use in your model tests.

• Use Factory Girl's associations to add a product to your item factory, and refactor your controller code.

Goal: Use test-driven development to implement the items controller.

• If you don't have one yet, use Rails to generate an rspec test file for the item controller. Run rspec spec/controllers, and debug any issues that prevent your item controller tests from running (you'll still see your product controller tests passing).

• Follow the examples in spec/controllers/products_controller_spec.rb as a guide while you write tests for your ItemsController.

• Your ItemsController doesn't need an #index method, since your app will display all of a product's items on the products#show page. However, it should have the other six methods for RESTful routes (#new, #create, #show, #edit, #update, and #destroy).

• Your tests should check that the appropriate controller actions display flash error messages when the model fails to validate the presence of the status attribute.

• As you go, continue to debug any errors that prevent rspec from running your tests. Read log and error messages carefully.

• Implement item controller code to pass the tests you wrote.

Goal: Update the product model with a new sell_through method.

• Making a change while doing TDD for an app? Better write tests first!

• Your goal is to add an instance method to the products model called sell_through. The #sell_through method should calculate and return a decimal value: the overall sell-through rate for this product (items sold / total items). Write the spec for #sell_through.

• Once you have the spec written, write code in your product model to pass the test(s) you wrote.

Part 3: Code Cleanup

Reference the solution-nested-items branch for guidance if you get stuck during this part of the lab.

Goal: Strong params for security and prosperity!

• If you haven't yet, use Rails strong parameters for your items and products controllers.

• In your products controller, define a private product_params method that implements strong parameters (look this up if you need to)! Refactor your controller actions to use the new product_params method.

• In your items controller, define a private item_params method that implements strong parameters (look this up if you need to)! Refactor your controller actions to use the new item_params method.

Goal: Don't Repeat Yourself in item and product lookup.

• Many routes in the products controller look up a product by id. Define a private set_product method in the products controller that assigns the @product variable based on the id parameter.

• Refactor your controller actions to use the set_product method before the other methods that find the product. Hint: look up before_filter.

• Similarly, many routes in the items controller look up a product and/or item. Create set_product and set_item methods in your items controller, and use before_filters to apply them to the appropriate actions.

Resources

• RSpec Rails Docs
• RSpec Controller Specs
• RSpec Built-In Matchers
• Factory Girl Rails Docs
• FFaker Docs
• FFaker Cheatsheet
• Rails Nested Resources