Test run on rails

Quote Rails Tutorial

What is a test?

The word is to make sure that the feature is implemented correctly. It's also a safety net when it comes to writing tests, and it's itself an "executable document" of your application's source code. With all the tests in place, you don't have to spend extra time chasing bugs, and if done right, it's definitely faster than without tests.

Benefits of testing

1. You can prevent regression bugs that may cause a malfunction.
2. You can safely refactor (improve) your code.
3. The test code acts as a client from the perspective of the application code, which is also useful when designing an application and deciding how to interface with other parts of the system.

Run the test

The test file is created when rails generate controller is executed in the terminal.

Terminal

#Example
$ rails generate controller StaticPages home help

↓

test/controllers/static_pages_controller_test.rb

require 'test_helper'

class StaticPagesControllerTest < ActionDispatch::IntegrationTest

  test "should get home"do ← home page test
    get static_pages_home_url ← Send GET request to home action
    assert_response :success ← The response to the request should be [Success]
  end

  test "should get help" do
    get static_pages_help_url
    assert_response :success
  end
end

↓

Terminal

$ rails db:migrate     #Required by some systems
$ rails test
2 tests, 2 assertions, 0 failures, 0 errors, 0 skips

The code is implemented without any problem because of 0 errors.

I try to make an error on purpose

Assuming you added the about page, try adding the code.

test/controllers/static_pages_controller_test.rb

require 'test_helper'

class StaticPagesControllerTest < ActionDispatch::IntegrationTest

  test "should get home" do
    get static_pages_home_url
    assert_response :success
  end

  test "should get help" do
    get static_pages_help_url
    assert_response :success
  end

  test "should get about" do
    get static_pages_about_url
    assert_response :success
  end
end

Test run

Terminal

$ rails test

NameError: undefined local variable or method `static_pages_about_url'
3 tests, 2 assertions, 0 failures, 1 errors, 0 skips

Error message if the URL to the About page cannot be found. Try modifying the routing file.

config/routes.rb

Rails.application.routes.draw do
  get  'static_pages/home'
  get  'static_pages/help'
  get  'static_pages/about'← Add
  root 'application#hello'
end

Test run

Terminal

$ rails test

AbstractController::ActionNotFound:
The action 'about' could not be found for StaticPagesController

Error message if there is no about action on the StaticPages controller. Try adding the about action.

app/controllers/static_pages_controller.rb

class StaticPagesController < ApplicationController

  def home
  end

  def help
  end

def about ← added
end ← added
end

Test run

Terminal

$ rails test
ActionController::UnknownFormat: StaticPagesController#about
is missing a template for this request format and variant.

Error message if there is no template (view). Create a view file with the following command or right-click.

Terminal

$ touch app/views/static_pages/about.html.erb

Test run

Terminal

$ rails test
3 tests, 3 assertions, 0 failures, 0 errors, 0 skips

The test is complete because it became 0 errors! !!

Refactor your code now that the tests are complete (This time it's done because there is no code to refactor)

This is called the "red / green / REFACTOR" cycle.