Fix test failures on Ruby 2.5 and add Windows testing

Signed-off-by: Tim Smith <tsmith@chef.io>

.expeditor/verify.pipeline.yml

@@ -10,7 +10,6 @@ expeditor:
       timeout_in_minutes: 30
 
 steps:
-
 - label: run-specs-ruby-2.5
   command:
     - .expeditor/run_linux_tests.sh rake
@@ -31,4 +30,13 @@ steps:
   expeditor:
     executor:
       docker:
-        image: ruby:2.7-buster
+        image: ruby:2.7-buster
+- label: run-specs-windows
+  command:
+    - bundle config --local path vendor/bundle
+    - bundle install --jobs=7 --retry=3 --without docs debug
+    - bundle exec rake
+  expeditor:
+    executor:
+      docker:
+        host_os: windows

Gemfile

@@ -14,11 +14,13 @@ group :test do
   gem "rspec-core"
   if Gem::Version.new(RUBY_VERSION) < Gem::Version.new("2.6")
     gem "chef-zero", "~> 14"
+    gem "chef", "~> 15"
+  else
+    gem "chef", ">= 15.0"
   end
   gem "rspec-expectations"
   gem "rspec-mocks"
   gem "rspec_junit_formatter"
   gem "fog-core"
   gem "chefstyle"
-  gem "chef", ">= 15.0"
 end