1 files changed, 123 insertions, 0 deletions
diff --git a/railties/lib/rails/generators/testing/behaviour.rb b/railties/lib/rails/generators/testing/behaviour.rb
new file mode 100644
index 0000000000..e0600d0b59
--- /dev/null
+++ b/railties/lib/rails/generators/testing/behaviour.rb
@@ -0,0 +1,123 @@
+require 'active_support/core_ext/class/attribute'
+require 'active_support/core_ext/module/delegation'
+require 'active_support/core_ext/hash/reverse_merge'
+require 'active_support/core_ext/kernel/reporting'
+require 'active_support/concern'
+require 'rails/generators'
+
+module Rails
+  module Generators
+    module Testing
+      module Behaviour
+        extend ActiveSupport::Concern
+
+        included do
+          class_attribute :destination_root, :current_path, :generator_class, :default_arguments
+
+          # Generators frequently change the current path using +FileUtils.cd+.
+          # So we need to store the path at file load and revert back to it after each test.
+          self.current_path = File.expand_path(Dir.pwd)
+          self.default_arguments = []
+        end
+
+        module ClassMethods
+          # Sets which generator should be tested:
+          #
+          #   tests AppGenerator
+          def tests(klass)
+            self.generator_class = klass
+          end
+
+          # Sets default arguments on generator invocation. This can be overwritten when
+          # invoking it.
+          #
+          #   arguments %w(app_name --skip-active-record)
+          def arguments(array)
+            self.default_arguments = array
+          end
+
+          # Sets the destination of generator files:
+          #
+          #   destination File.expand_path("../tmp", File.dirname(__FILE__))
+          def destination(path)
+            self.destination_root = path
+          end
+        end
+
+        # Runs the generator configured for this class. The first argument is an array like
+        # command line arguments:
+        #
+        #   class AppGeneratorTest < Rails::Generators::TestCase
+        #     tests AppGenerator
+        #     destination File.expand_path("../tmp", File.dirname(__FILE__))
+        #     teardown :cleanup_destination_root
+        #
+        #     test "database.yml is not created when skipping Active Record" do
+        #       run_generator %w(myapp --skip-active-record)
+        #       assert_no_file "config/database.yml"
+        #     end
+        #   end
+        #
+        # You can provide a configuration hash as second argument. This method returns the output
+        # printed by the generator.
+        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
+
+        # 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
+
+        # Create a Rails::Generators::GeneratedAttribute by supplying the
+        # attribute type and, optionally, the attribute name:
+        #
+        #   create_generated_attribute(:string, 'name')
+        def create_generated_attribute(attribute_type, name = 'test', index = nil)
+          Rails::Generators::GeneratedAttribute.parse([name, attribute_type, index].compact.join(':'))
+        end
+
+        protected
+
+          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:
+            cd current_path
+          end
+
+          def prepare_destination # :nodoc:
+            rm_rf(destination_root)
+            mkdir_p(destination_root)
+          end
+
+          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 capture(stream)
+            stream = stream.to_s
+            captured_stream = Tempfile.new(stream)
+            stream_io = eval("$#{stream}")
+            origin_stream = stream_io.dup
+            stream_io.reopen(captured_stream)
+
+            yield
+
+            stream_io.rewind
+            return captured_stream.read
+          ensure
+            captured_stream.close
+            captured_stream.unlink
+            stream_io.reopen(origin_stream)
+          end
+      end
+    end
+  end
+end