We should not include engine.rake file into rake

if we are passing -T which is skip_test_unit

See issue #6673 for more details.

I saw that we are not creating dummy app even if
we do skip_test_unit.

Fixes #6673

railties/lib/rails/generators/rails/plugin_new/templates/Rakefile

@@ -14,7 +14,7 @@ RDoc::Task.new(:rdoc) do |rdoc|
   rdoc.rdoc_files.include('lib/**/*.rb')
 end
 
-<% if full? && !options[:skip_active_record] -%>
+<% if full? && !options[:skip_active_record] && !options[:skip_test_unit] -%>
 APP_RAKEFILE = File.expand_path("../<%= dummy_path -%>/Rakefile", __FILE__)
 load 'rails/tasks/engine.rake'
 <% end %>

railties/test/generators/plugin_new_generator_test.rb

@@ -58,6 +58,14 @@ def test_generating_test_files_in_full_mode
     assert_file "test/integration/navigation_test.rb", /ActionDispatch::IntegrationTest/
   end
 
+  def test_generating_test_files_in_full_mode_without_unit_test_files
+    run_generator [destination_root, "-T", "--full"]
+
+    assert_no_directory "test/integration/"
+    assert_no_file "test"
+    assert_no_match(/APP_RAKEFILE/, File.read(File.join(destination_root, "Rakefile")))
+  end
+
   def test_ensure_that_plugin_options_are_not_passed_to_app_generator
     FileUtils.cd(Rails.root)
     assert_no_match(/It works from file!.*It works_from_file/, run_generator([destination_root, "-m", "lib/template.rb"]))