Appreciating Rails test scaffolds

When using the generate scaffold command from Rails it will also generate a controller and a system test. It's worth paying attention to these instead of just discarding them. They are a useful learning tool for a few reasons.

They immediately provide free test coverage for the happy path
They help guide towards Rails conventions - simple controller tests that test the entire request
They help teach you how to use Minitest

Controller test

require "test_helper"

class PostsControllerTest < ActionDispatch::IntegrationTest
  setup do
    @post = posts(:one)
  end

  test "should get index" do
    get posts_url
    assert_response :success
  end

  test "should get new" do
    get new_post_url
    assert_response :success
  end

  test "should create post" do
    assert_difference("Post.count") do
      post posts_url, params: { post: { title: @post.title } }
    end

    assert_redirected_to post_url(Post.last)
  end

  test "should show post" do
    get post_url(@post)
    assert_response :success
  end

  test "should get edit" do
    get edit_post_url(@post)
    assert_response :success
  end

  test "should update post" do
    patch post_url(@post), params: { post: { title: @post.title } }
    assert_redirected_to post_url(@post)
  end

  test "should destroy post" do
    assert_difference("Post.count", -1) do
      delete post_url(@post)
    end

    assert_redirected_to posts_url
  end
end

System test

require "application_system_test_case"

class PostsTest < ApplicationSystemTestCase
  setup do
    @post = posts(:one)
  end

  test "visiting the index" do
    visit posts_url
    assert_selector "h1", text: "Posts"
  end

  test "should create post" do
    visit posts_url
    click_on "New post"

    fill_in "Title", with: @post.title
    click_on "Create Post"

    assert_text "Post was successfully created"
    click_on "Back"
  end

  test "should update Post" do
    visit post_url(@post)
    click_on "Edit this post", match: :first

    fill_in "Title", with: @post.title
    click_on "Update Post"

    assert_text "Post was successfully updated"
    click_on "Back"
  end

  test "should destroy Post" do
    visit post_url(@post)
    click_on "Destroy this post", match: :first

    assert_text "Post was successfully destroyed"
  end
end

Minitest on Rails.

Appreciating Rails test scaffolds

Controller test

System test