Add support for RSpec to previews as test cases (#1408)

* Add rspec-rails gem

* Add support for render_previews in RSpec tests

* Enable RSpec tests on CI

* Update lib/view_component/render_preview_helper.rb

* Update lib/view_component/render_preview_helper.rb

* Update Gemfile

Co-authored-by: Joel Hawksley <joelhawksley@github.com>

.github/workflows/ci.yml

@@ -61,7 +61,7 @@ jobs:
       run: |
         bundle config path vendor/bundle
         bundle update
-        bundle exec rake
+        bundle exec rake test spec
       env:
         RAISE_ON_WARNING: 1
         MEASURE_COVERAGE: true

.rspec

@@ -0,0 +1 @@
+--require spec_helper

Gemfile

@@ -7,6 +7,7 @@ rails_version = (ENV["RAILS_VERSION"] || "~> 7.0.0").to_s
 
 gem "capybara", "~> 3"
 gem "rails", rails_version == "main" ? {git: "https://github.com/rails/rails", ref: "main"} : rails_version
+gem "rspec-rails", "~> 5"
 
 if RUBY_VERSION >= "3.1"
   gem "net-imap", require: false

Gemfile.lock

@@ -103,6 +103,7 @@ GEM
     coderay (1.1.3)
     concurrent-ruby (1.1.10)
     crass (1.0.6)
+    diff-lcs (1.5.0)
     digest (3.1.0)
     docile (1.4.0)
     erb_lint (0.0.37)
@@ -193,6 +194,23 @@ GEM
     rake (13.0.6)
     regexp_parser (2.4.0)
     rexml (3.2.5)
+    rspec-core (3.11.0)
+      rspec-support (~> 3.11.0)
+    rspec-expectations (3.11.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.11.0)
+    rspec-mocks (3.11.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.11.0)
+    rspec-rails (5.1.2)
+      actionpack (>= 5.2)
+      activesupport (>= 5.2)
+      railties (>= 5.2)
+      rspec-core (~> 3.10)
+      rspec-expectations (~> 3.10)
+      rspec-mocks (~> 3.10)
+      rspec-support (~> 3.10)
+    rspec-support (3.11.0)
     rubocop (1.13.0)
       parallel (~> 1.10)
       parser (>= 3.0.0.0)
@@ -268,6 +286,7 @@ DEPENDENCIES
   pry (~> 0.13)
   rails (~> 7.0.0)
   rake (~> 13.0)
+  rspec-rails (~> 5)
   simplecov (~> 0.18.0)
   simplecov-console (~> 0.7.2)
   slim (~> 4.0)

Rakefile

@@ -11,6 +11,12 @@ Rake::TestTask.new(:test) do |t|
   t.test_files = FileList["test/**/*_test.rb"]
 end
 
+begin
+  require "rspec/core/rake_task"
+  RSpec::Core::RakeTask.new(:spec)
+rescue LoadError
+end
+
 desc "Runs benchmarks against components"
 task :partial_benchmark do
   ruby "./performance/partial_benchmark.rb"

docs/CHANGELOG.md

@@ -9,6 +9,10 @@ title: Changelog
 
 ## main
 
+* Add support for `render_preview` in RSpec tests.
+
+    *Thomas Hutterer*
+
 ## 2.59.0
 
 * Expose Capybara DSL methods directly inside tests.

gemfiles/rails_6.0.gemfile

@@ -4,6 +4,7 @@ source "https://rubygems.org"
 
 gem "capybara", "~> 3"
 gem "rails", "~> 6.0.0"
+gem "rspec-rails", "~> 5.1"
 gem "tailwindcss-rails", "~> 2.0"
 
 gemspec path: "../"

gemfiles/rails_6.1.gemfile

@@ -4,6 +4,7 @@ source "https://rubygems.org"
 
 gem "capybara", "~> 3"
 gem "rails", "~> 6.1.0"
+gem "rspec-rails", "~> 5.1"
 gem "tailwindcss-rails", "~> 2.0"
 gem "net-smtp", require: false
 gem "net-imap", require: false

gemfiles/rails_7.0.gemfile

@@ -4,6 +4,7 @@ source "https://rubygems.org"
 
 gem "capybara", "~> 3"
 gem "rails", "~> 7.0.0"
+gem "rspec-rails", "~> 5.1"
 gem "tailwindcss-rails", "~> 2.0"
 
 gemspec path: "../"

gemfiles/rails_head.gemfile

@@ -4,6 +4,7 @@ source "https://rubygems.org"
 
 gem "capybara", "~> 3"
 gem "rails", github: "rails/rails", branch: "main"
+gem "rspec-rails", "~> 5.1"
 gem "tailwindcss-rails", "~> 2.0"
 
 gemspec path: "../"

lib/view_component/render_preview_helper.rb

@@ -15,11 +15,21 @@ module ViewComponent
     #
     # MyComponentTest -> MyComponentPreview etc.
     #
+    # In RSpec, `Preview` is appended to `described_class`.
+    #
     # @param preview [String] The name of the preview to be rendered.
     # @return [Nokogiri::HTML]
     def render_preview(name)
       begin
-        preview_klass = self.class.name.gsub("Test", "Preview")
+        preview_klass = if respond_to?(:described_class)
+          if described_class.nil?
+            raise "`render_preview` expected a described_class, but it is nil."
+          end
+
+          "#{described_class}Preview"
+        else
+          self.class.name.gsub("Test", "Preview")
+        end
         preview_klass = preview_klass.constantize
       rescue NameError
         raise NameError.new(

spec/sandbox

@@ -0,0 +1 @@
+../test/sandbox

spec/spec_helper.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require "simplecov"
+require "simplecov-console"
+
+if ENV["MEASURE_COVERAGE"]
+  SimpleCov.start do
+    command_name "rails#{ENV["RAILS_VERSION"]}-ruby#{ENV["RUBY_VERSION"]}" if ENV["RUBY_VERSION"]
+
+    formatter SimpleCov::Formatter::Console
+  end
+end
+
+require "bundler/setup"
+
+# Configure Rails Environment
+ENV["RAILS_ENV"] = "test"
+
+require "view_component/deprecation"
+ViewComponent::Deprecation.behavior = :silence
+
+require File.expand_path("../sandbox/config/environment.rb", __FILE__)
+require "rspec/rails"
+
+RSpec.configure do |config|
+  config.include ViewComponent::TestHelpers
+end

test/sandbox/spec/components/previews/preview_component_spec.rb

@@ -0,0 +1,25 @@
+describe PreviewComponent do
+  include ViewComponent::RenderPreviewHelper
+
+  before do
+    ViewComponent::Preview.load_previews
+  end
+
+  it "renders the preview" do
+    render_preview(:default)
+
+    expect(page).to have_css "h1", text: "Lorem Ipsum"
+  end
+end
+
+describe "PreviewComponent" do
+  include ViewComponent::RenderPreviewHelper
+
+  before do
+    ViewComponent::Preview.load_previews
+  end
+
+  it "raises an error" do
+    expect { render_preview(:default) }.to raise_error(/expected a described_class/)
+  end
+end