```ruby
require 'simplecov'
SimpleCov.start

# Configure Rails Environment
ENV['RAILS_ENV'] = 'test'

# require File.expand_path("../dummy/config/environment.rb",  __FILE__)
require File.expand_path('../rails421/config/environment.rb', __FILE__)
require 'rails/test_help'

Rails.backtrace_cleaner.remove_silencers!

# Load support files
Dir["#{File.dirname(__FILE__)}/support/**/*.rb"].each { |f| require f }

# Load fixtures from the engine
if ActiveSupport::TestCase.method_defined?(:fixture_path=)
  ActiveSupport::TestCase.fixture_path = File.expand_path('../fixtures', __FILE__)
end
```

Use the installed Rails 6.1 application for tests
user
```ruby
require 'simplecov'
SimpleCov.start

# Configure Rails Environment
ENV['RAILS_ENV'] = 'test'

# require File.expand_path("../dummy/config/environment.rb",  __FILE__)
require File.expand_path('../rails610/config/environment.rb', __FILE__)
require 'rails/test_help'

Rails.backtrace_cleaner.remove_silencers!

# Load support files
Dir["#{File.dirname(__FILE__)}/support/**/*.rb"].each { |f| require f }

# Load fixtures from the engine
if ActiveSupport::TestCase.method_defined?(:fixture_path=)
  ActiveSupport::TestCase.fixture_path = File.expand_path('../fixtures', __FILE__)
end
```
assistant