Test shared behavior of installer commands

This adds test coverage for the shared behavior of the installer
commands.  The commands are tested against a freshly generated Rails app
using the version of Rails that is currently loaded.  Thus the
installers can be tested with different versions of Rails in CI.

.gitignore

@@ -1,3 +1,4 @@
+/tmp/
 .byebug_history
 *.gem
 

test/bootstrap_installer_test.rb

@@ -0,0 +1,13 @@
+require "test_helper"
+require_relative "shared_installer_tests"
+
+class BootstrapInstallerTest < ActiveSupport::TestCase
+  include RailsAppHelpers
+  include SharedInstallerTests
+
+  private
+    def run_installer
+      stub_bins("gem", "yarn", "npm")
+      run_command("bin/rails", "css:install:bootstrap")
+    end
+end

test/bulma_installer_test.rb

@@ -0,0 +1,13 @@
+require "test_helper"
+require_relative "shared_installer_tests"
+
+class BulmaInstallerTest < ActiveSupport::TestCase
+  include RailsAppHelpers
+  include SharedInstallerTests
+
+  private
+    def run_installer
+      stub_bins("gem", "yarn", "npm")
+      run_command("bin/rails", "css:install:bulma")
+    end
+end

test/postcss_installer_test.rb

@@ -0,0 +1,13 @@
+require "test_helper"
+require_relative "shared_installer_tests"
+
+class PostcssInstallerTest < ActiveSupport::TestCase
+  include RailsAppHelpers
+  include SharedInstallerTests
+
+  private
+    def run_installer
+      stub_bins("gem", "yarn", "npm")
+      run_command("bin/rails", "css:install:postcss")
+    end
+end

test/sass_installer_test.rb

@@ -0,0 +1,13 @@
+require "test_helper"
+require_relative "shared_installer_tests"
+
+class SassInstallerTest < ActiveSupport::TestCase
+  include RailsAppHelpers
+  include SharedInstallerTests
+
+  private
+    def run_installer
+      stub_bins("gem", "yarn", "npm")
+      run_command("bin/rails", "css:install:sass")
+    end
+end

test/shared_installer_tests.rb

@@ -0,0 +1,123 @@
+require "json"
+
+module SharedInstallerTests
+  extend ActiveSupport::Concern
+
+  included do
+    test "basic installation with pre-existing files" do
+      with_new_rails_app do
+        File.write(".gitignore", "# pre-existing\n", mode: "a+")
+        File.write("package.json", %({ "name": "pre-existing" }\n))
+        File.write("Procfile.dev", "pre: existing\n", mode: "a+")
+
+        run_installer
+
+        assert_equal 0, File.size("app/assets/builds/.keep")
+
+        File.read(".gitignore").tap do |gitignore|
+          assert_match "# pre-existing", gitignore
+          assert_match "/app/assets/builds/*\n!/app/assets/builds/.keep", gitignore
+          assert_match "/node_modules", gitignore
+        end
+
+        JSON.load_file("package.json").tap do |package_json|
+          assert_equal "pre-existing", package_json["name"]
+        end
+
+        assert_not File.exist?("app/assets/stylesheets/application.css")
+
+        File.read("Procfile.dev").tap do |procfile|
+          assert_match "pre: existing", procfile
+          assert_match "css: yarn", procfile
+        end
+
+        File.read("bin/dev").tap do |bin_dev|
+          assert_equal File.read("#{__dir__}/../lib/install/dev"), bin_dev
+          assert_equal 0700, File.stat("bin/dev").mode & 0700
+        end
+      end
+    end
+
+    test "basic installation without pre-existing files" do
+      with_new_rails_app do
+        FileUtils.rm("app/views/layouts/application.html.erb")
+        FileUtils.rm(".gitignore")
+        FileUtils.rm_rf("package.json")
+        FileUtils.rm_rf("Procfile.dev")
+
+        out, _err = run_installer
+
+        assert_not File.exist?("app/views/layouts/application.html.erb")
+        assert_match "Add <%= stylesheet_link_tag", out
+
+        assert_not File.exist?(".gitignore")
+
+        assert_instance_of Hash, JSON.load_file("package.json")
+
+        File.read("Procfile.dev").tap do |procfile|
+          assert_match "css: yarn", procfile
+        end
+
+        assert_match "STUBBED gem install foreman", out
+      end
+    end
+
+    test "basic installation with Sprockets" do
+      with_new_rails_app(*("--asset-pipeline=sprockets" if Rails::VERSION::MAJOR >= 7)) do
+        File.write("app/assets/config/manifest.js", "// pre-existing\n", mode: "a+")
+
+        run_installer
+
+        File.read("app/assets/config/manifest.js").tap do |sprockets_manifest|
+          assert_match "// pre-existing", sprockets_manifest
+          assert_match "//= link_tree ../builds", sprockets_manifest
+          assert_no_match "//= link_directory ../stylesheets .css", sprockets_manifest
+        end
+      end
+    end
+
+    if Rails::VERSION::MAJOR == 7
+      test "basic installation with Propshaft" do
+        with_new_rails_app("--asset-pipeline=propshaft") do
+          run_installer
+
+          assert_not File.exist?("app/assets/config/manifest.js")
+        end
+      end
+    end
+
+    if Rails::VERSION::MAJOR >= 7
+      test "basic installation with Turbo" do
+        with_new_rails_app do
+          run_installer
+
+          File.read("app/views/layouts/application.html.erb").tap do |layout|
+            assert_match %(<%= stylesheet_link_tag "application", "data-turbo-track": "reload" %>), layout[%r{<head.*</head>}m]
+          end
+        end
+      end
+    end
+
+    test "basic installation without Turbo" do
+      with_new_rails_app(*("--skip-hotwire" if Rails::VERSION::MAJOR >= 7)) do
+        run_installer
+
+        File.read("app/views/layouts/application.html.erb").tap do |layout|
+          assert_match %(<%= stylesheet_link_tag "application" %>), layout[%r{<head.*</head>}m]
+        end
+      end
+    end
+
+    test "basic installation with Bun" do
+      with_new_rails_app do
+        stub_bins("bun")
+
+        run_installer
+
+        File.read("Procfile.dev").tap do |procfile|
+          assert_match "css: bun run", procfile
+        end
+      end
+    end
+  end
+end

test/tailwind_installer_test.rb

@@ -0,0 +1,13 @@
+require "test_helper"
+require_relative "shared_installer_tests"
+
+class TailwindInstallerTest < ActiveSupport::TestCase
+  include RailsAppHelpers
+  include SharedInstallerTests
+
+  private
+    def run_installer
+      stub_bins("gem", "yarn", "npm")
+      run_command("bin/rails", "css:install:tailwind")
+    end
+end

test/test_helper.rb

@@ -4,3 +4,68 @@
 require "fileutils"
 require "rails"
 require "rails/test_help"
+
+module RailsAppHelpers
+  def self.included(base)
+    base.include ActiveSupport::Testing::Isolation
+  end
+
+  private
+    def create_new_rails_app(app_dir, *cli_options)
+      require "rails/generators/rails/app/app_generator"
+      Rails::Generators::AppGenerator.start([app_dir, "--skip-bundle", "--skip-bootsnap", "--quiet", cli_options].flatten)
+
+      Dir.chdir(app_dir) do
+        gemfile = File.read("Gemfile")
+
+        gemfile.gsub!(/^gem ["']cssbundling-rails["'].*/, "")
+        gemfile << %(gem "cssbundling-rails", path: #{File.expand_path("..", __dir__).inspect}\n)
+
+        if Rails::VERSION::PRE == "alpha"
+          gemfile.gsub!(/^gem ["']rails["'].*/, "")
+          gemfile << %(gem "rails", path: #{Gem.loaded_specs["rails"].full_gem_path.inspect}\n)
+        end
+
+        File.write("Gemfile", gemfile)
+
+        run_command("bundle", "install")
+      end
+    end
+
+    def with_new_rails_app(*cli_options, &block)
+      require "digest/sha1"
+      variant = [RUBY_VERSION, Gem.loaded_specs["rails"].full_gem_path, cli_options.flatten.sort]
+      app_name = "app_#{Digest::SHA1.hexdigest(variant.to_s)}"
+      cache_dir = "#{__dir__}/../tmp"
+      FileUtils.mkdir_p(cache_dir)
+
+      Dir.mktmpdir do |tmpdir|
+        if Dir.exist?("#{cache_dir}/#{app_name}")
+          FileUtils.cp_r("#{cache_dir}/#{app_name}", tmpdir)
+        else
+          create_new_rails_app("#{tmpdir}/#{app_name}", *cli_options)
+          FileUtils.cp_r("#{tmpdir}/#{app_name}", cache_dir) # Cache app for future runs.
+        end
+
+        Dir.chdir("#{tmpdir}/#{app_name}", &block)
+      end
+    end
+
+    def stub_bins(*names)
+      names.each do |name|
+        File.write("bin/#{name}", <<~BASH)
+          #!/usr/bin/env bash
+          echo STUBBED #{name} "$@"
+        BASH
+
+        FileUtils.chmod(0755, "bin/#{name}")
+      end
+    end
+
+    def run_command(*command)
+      Bundler.with_unbundled_env do
+        env = { "PATH" => "bin:#{ENV["PATH"]}" }
+        capture_subprocess_io { system(env, *command, exception: true) }
+      end
+    end
+end