To implement, write the test and then code the process

background </ font>

Although it is in the field, I think that development usually proceeds according to the following flow. (1) Design-> (2) Processing coding-> (3) Test coding-> (4) Unit testing, etc ...

But in the Rails tutorial, (1) Design → (2) Test coding → (3) Processing coding… It was explained in the flow. I learned a little, so I will post it as an article.

environment </ font>

item Contents
OS aws #35-Ubuntu SMP(Cloud9)
Ruby ruby 2.6.3p62 (2019-04-16 revision 67580)
Ruby On Rails Rails 6.0.3

supported </ font>

The following is an example of coding from the test source when adding a new about (overview) page to an app with routing and controller settings.

config/route.rb


Rails.application.routes.draw do
  get 'static_pages/home'
  get 'static_pages/help'
  root 'static_pages#home'
* The routing of the overview page has not been set yet.
end

app/controller/static_pages_controller.rb


class StaticPagesController < ApplicationController
  def home
  end

  def help
  end
   
* The action on the summary page has not been set yet.
end

Step 1) Here, write a test for the newly added page in advance.

test/static_pages_controller_test.rb


require 'test_helper'

class StaticPagesControllerTest < ActionDispatch::IntegrationTest
1   
2   test "should get home" do
3     get static_pages_home_url
4     assert_response :success
5   end
6 
7   test "should get help" do
8     get static_pages_help_url
9     assert_response :success
10  end
11
12 ※~~~~From here, fill in the test on the summary page assuming.~~~~
13  test "should get about" do
14    get static_pages_about_url
15    assert_response :success
16  end

end

Step 2) Try to execute the test (1st time = error occurs because the process has not been described yet)

$rails test

Error:
StaticPagesControllerTest#test_should_get_about:
NameError: undefined local variable or method `static_pages_about_url' 
..

Finished in 2.157942s, 1.3902 runs/s, 0.9268 assertions/s.
3 runs, 2 assertions, 0 failures, 1 errors, 0 skips

I got a error. </ font>

Step 3) From the above, the path does not pass, so review the routing.

config/route.rb


Rails.application.routes.draw do
  get 'static_pages/home'
  get 'static_pages/help'
  get 'static_pages/about'← Added here ☆
  root 'static_pages#home'
end

Step 4) Execute the test (2nd time = an error will occur on the assumption)

$ rails test

Error:
StaticPagesControllerTest#test_should_get_about:
AbstractController::ActionNotFound: The action 'about' could not be found for StaticPagesController…
3 runs, 2 assertions, 0 failures, 1 errors, 0 skips

I got an error again. </ font>

Step 5) From the above error, review the controller because the action is the cause.

app/controller/static_pages_controller.rb


class StaticPagesController < ApplicationController
  def home
  end

  def help
  end

def about ← Added here ☆
  end

end

Step 6) Try running more tests (3rd time = what happens ...)

$ rails test

Error:
StaticPagesControllerTest#test_should_get_about:
ActionController::MissingExactTemplate: StaticPagesController#about is missing a template for request formats: ..
3 runs, 2 assertions, 0 failures, 1 errors, 0 skips

I got an error again. Next time, the wording seems to be different ... </ font>

Step 7) From the above error, it seems that the template is the cause, so add a view.

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

Step 8) Execute the test (4th time = normal test pass)

$ rails test

...
3 runs, 3 assertions, 0 failures, 0 errors, 0

It went well ... It's the basics of the basics, but I felt that it should be included in the refactoring. </ font>

References </ font>

Tutorial. Start with testing

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