```ruby
require "rubygems"

# Set ENV['BUNDLE_GEMFILE'] as follows:
#
# Our test dummy app uses `enum`, so it must use AR >= 4.1. However, we want our
# gemspec to support AR >= 4.0. For local test runs, using our root Gemfile
# would be problematic here. For TravisCI it seems to be fine. Maybe Travis
# overwrites the root Gemfile?
if ENV.key?("BUNDLE_GEMFILE")
  # This is a local test run, and we are running rake tasks in this dummy app,
  # and we can't use the project's root Gemfile for the reasons given above.
  puts "Booting PT test dummy app: Using BUNDLE_GEMFILE: #{ENV.fetch('BUNDLE_GEMFILE')}"
else
  gemfile = File.expand_path("../../../../Gemfile", __FILE__)
  if File.exist?(gemfile)
    puts "Booting PT test dummy app: Using gemfile: #{gemfile}"
    ENV["BUNDLE_GEMFILE"] = gemfile
  end
end
require "bundler"
Bundler.setup

$LOAD_PATH.unshift(File.expand_path("../../../../lib", __FILE__))
```

Remove debugging output from test suite
user
```ruby
require "rubygems"

# We normally use the root project Gemfile (and gemspec), but when we run rake
# locally (not on travis) in this dummy app, we set the BUNDLE_GEMFILE env.
# variable. The project Gemfile/gemspec allows AR 4.0, which is a problem
# because this dummy app uses `enum` in some of its models, and `enum` was
# introduced in AR 4.1. So, when we run rake here, we use:
#
#     BUNDLE_GEMFILE=../../gemfiles/ar_4.2.gemfile bundle exec rake
#
# Once we drop support for AR 4.0 and 4.1 this will be less of a problem, but
# we should keep the ability to specify BUNDLE_GEMFILE because the same
# situation could come up in the future.
unless ENV.key?("BUNDLE_GEMFILE")
  gemfile = File.expand_path("../../../../Gemfile", __FILE__)
  if File.exist?(gemfile)
    puts "Booting PT test dummy app: Using gemfile: #{gemfile}"
    ENV["BUNDLE_GEMFILE"] = gemfile
  end
end
require "bundler"
Bundler.setup

$LOAD_PATH.unshift(File.expand_path("../../../../lib", __FILE__))
```
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