module Rails::Generators::Testing::Behaviour

def create_generated_attribute(attribute_type, name = 'test', index = nil)

create_generated_attribute(:string, 'name')

attribute type and, optionally, the attribute name:
Create a Rails::Generators::GeneratedAttribute by supplying the 
def create_generated_attribute(attribute_type, name = 'test', index = nil)
  Rails::Generators::GeneratedAttribute.parse([name, attribute_type, index].compact.join(':'))
end

def destination_root_is_set? # :nodoc:

:nodoc: 
def destination_root_is_set? # :nodoc:
  raise "You need to configure your Rails::Generators::TestCase destination root." unless destination_root
end

def ensure_current_path # :nodoc:

:nodoc: 
def ensure_current_path # :nodoc:
  cd current_path
end

def generator(args=self.default_arguments, options={}, config={})

Instantiate the generator. 
def generator(args=self.default_arguments, options={}, config={})
  @generator ||= self.generator_class.new(args, options, config.reverse_merge(destination_root: destination_root))
end

def migration_file_name(relative) # :nodoc:

:nodoc: 
def migration_file_name(relative) # :nodoc:
  absolute = File.expand_path(relative, destination_root)
  dirname, file_name = File.dirname(absolute), File.basename(absolute).sub(/\.rb$/, '')
  Dir.glob("#{dirname}/[0-9]*_*.rb").grep(/\d+_#{file_name}.rb$/).first
end

def prepare_destination

Clears all files and directories in destination. 
def prepare_destination
  rm_rf(destination_root)
  mkdir_p(destination_root)
end

def run_generator(args=self.default_arguments, config={})

printed by the generator.
You can provide a configuration hash as second argument. This method returns the output

end
end
assert_no_file "config/database.yml"
run_generator %w(myapp --skip-active-record)
test "database.yml is not created when skipping Active Record" do

setup :prepare_destination
destination File.expand_path("../tmp", File.dirname(__FILE__))
tests AppGenerator
class AppGeneratorTest < Rails::Generators::TestCase

command line arguments:
Runs the generator configured for this class. The first argument is an array like 
def run_generator(args=self.default_arguments, config={})
  capture(:stdout) do
    args += ['--skip-bundle'] unless args.include? '--dev'
    self.generator_class.start(args, config.reverse_merge(destination_root: destination_root))
  end
end