From 3fb6c9f5f390ccc7a6bffec681e51f0acba803f1 Mon Sep 17 00:00:00 2001
From: DualFroz <me@dualfroz.com>
Date: Fri, 11 Sep 2026 13:23:03 +0200
Subject: [PATCH] test: cover MailerPreviewAppTest and welcome

---
 test/test_mailer_preview_app.rb | 100 ++++++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)
 create mode 100644 test/test_mailer_preview_app.rb

diff --git a/test/test_mailer_preview_app.rb b/test/test_mailer_preview_app.rb
new file mode 100644
index 0000000..8729002
--- /dev/null
+++ b/test/test_mailer_preview_app.rb
@@ -0,0 +1,100 @@
+require 'minitest/autorun'
+require 'prism'
+require 'support'
+require 'tmpdir'
+require 'fileutils'
+
+class MailerPreviewAppTest < Minitest::Test
+  include TestSupport
+
+  def setup
+    @dir = Dir.mktmpdir('prism-mailer-preview-app')
+    FileUtils.mkdir_p(File.join(@dir, 'preview_widget'))
+    File.write(File.join(@dir, 'preview_widget/welcome.text.erb'), "Hi <%= name %>\n")
+    File.write(File.join(@dir, 'preview_widget/welcome.html.erb'), "<p>Hi <%= name %></p>\n")
+
+    mailer_dir = @dir
+    @mailer_class = Class.new(Prism::Mailer::Base) do
+      self.template_roots = [mailer_dir]
+
+      def welcome(name)
+        @name = name
+        mail(to: 'someone@example.com', from: 'app@example.com', subject: 'Welcome!')
+      end
+    end
+    Object.const_set(:PreviewWidgetMailer, @mailer_class)
+
+    mailer_class = @mailer_class
+    @preview_class = Class.new(Prism::Mailer::Preview) do
+      define_method(:welcome) { mailer_class.welcome('Fixture Fred') }
+    end
+    Object.const_set(:WidgetMailerPreview, @preview_class)
+
+    @app = Prism::Mailer::PreviewApp.new
+  end
+
+  def teardown
+    Prism::Mailer::Preview.registry.delete(@preview_class)
+    %i[WidgetMailerPreview PreviewWidgetMailer].each do |name|
+      Object.send(:remove_const, name) if Object.const_defined?(name)
+    end
+    FileUtils.remove_entry(@dir)
+  end
+
+  def call(path, script_name: '')
+    env = env_for('GET', path)
+    env['SCRIPT_NAME'] = script_name
+    @app.call(env)
+  end
+
+  def test_index_lists_registered_previews
+    status, _, body = call('/')
+    assert_equal 200, status
+    assert_includes body.join, 'widget_mailer'
+  end
+
+  def test_preview_page_lists_its_email_actions
+    status, _, body = call('/widget_mailer')
+    assert_equal 200, status
+    assert_includes body.join, 'welcome'
+  end
+
+  def test_email_page_renders_the_actual_rendered_html_body
+    status, headers, body = call('/widget_mailer/welcome')
+    assert_equal 200, status
+    assert_equal 'text/html; charset=UTF-8', headers['Content-Type']
+    assert_includes body.join, '<p>Hi Fixture Fred</p>'
+    assert_includes body.join, 'Welcome!'
+  end
+
+  def test_email_page_never_delivers_the_message
+    Prism::Mailer.deliveries.clear
+    call('/widget_mailer/welcome')
+    assert_empty Prism::Mailer.deliveries
+  end
+
+  def test_unknown_preview_is_a_404
+    status, = call('/does_not_exist')
+    assert_equal 404, status
+  end
+
+  def test_unknown_email_action_is_a_404
+    status, = call('/widget_mailer/does_not_exist')
+    assert_equal 404, status
+  end
+
+  def test_links_are_built_from_script_name_so_mounting_anywhere_works
+    _, _, body = call('/', script_name: '/rails/mailers')
+    assert_includes body.join, 'href="/rails/mailers/widget_mailer"'
+  end
+
+  def test_mounted_end_to_end_through_an_application
+    host_app = Class.new(Prism::Application) do
+      mount '/rails/mailers', Prism::Mailer::PreviewApp.new
+    end
+
+    status, _, body = host_app.call(env_for('GET', '/rails/mailers/widget_mailer/welcome'))
+    assert_equal 200, status
+    assert_includes body.join, '<p>Hi Fixture Fred</p>'
+  end
+end