diff --git a/bin/cuffdown b/bin/cuffdown
index 57b93e5..20abe50 100755
--- a/bin/cuffdown
+++ b/bin/cuffdown
@@ -1,55 +1,5 @@
 #!/usr/bin/env ruby
 
-require 'cuffsert/metadata'
-require 'cuffsert/rxcfclient'
-require 'yaml'
+require 'cuffdown/main'
 
-module CuffDown
-  def self.parameters(stack)
-    (stack[:parameters] || []).map do |param|
-      {
-        'Name' => param[:parameter_key],
-        'Value' => param[:parameter_value],
-      }
-    end
-  end
-
-  def self.tags(stack)
-    (stack[:tags] || []).map do |param|
-      {
-        'Name' => param[:key],
-        'Value' => param[:value],
-      }
-    end
-  end
-
-  def self.dump(name, params, tags, output)
-    result = {
-      'Format' => 'v1',
-      'Suffix' => name,
-      'Parameters' => params,
-      'Tags' => tags,
-    }
-    YAML.dump(result, output)
-  end
-
-  def self.run(args)
-    meta = CuffSert::StackConfig.new
-    meta.stackname = args[0]
-    client = CuffSert::RxCFClient.new
-    stack = client.find_stack_blocking(meta)
-    unless stack
-      STDERR.puts "No such stack #{meta.stackname}"
-      exit(1)
-    end
-    stack = stack.to_h
-    self.dump(
-      stack[:stack_name],
-      self.parameters(stack),
-      self.tags(stack),
-      STDOUT
-    )
-  end
-end
-
-CuffDown.run(ARGV)
+CuffDown.run(ARGV, STDOUT)
diff --git a/lib/cuffbase.rb b/lib/cuffbase.rb
index 7a688fa..e564ce6 100644
--- a/lib/cuffbase.rb
+++ b/lib/cuffbase.rb
@@ -1,6 +1,12 @@
 require 'yaml'
 
 module CuffBase
+  def self.shared_cli_args(opts, args)
+    opts.on('--region=aws_region', 'AWS region, overrides env variable AWS_REGION') do |region|
+      args[:aws_region] = region
+    end
+  end
+
   def self.empty_from_template(io)
     self.template_parameters(io) {|_| nil }
   end
diff --git a/lib/cuffdown/main.rb b/lib/cuffdown/main.rb
new file mode 100644
index 0000000..a1dc363
--- /dev/null
+++ b/lib/cuffdown/main.rb
@@ -0,0 +1,67 @@
+require 'cuffbase'
+require 'cuffsert/metadata'
+require 'cuffsert/rxcfclient'
+require 'optparse'
+require 'yaml'
+
+module CuffDown
+  def self.parse_cli_args(argv)
+    args = {}
+    parser = OptionParser.new do |opts|
+      opts.banner = 'Output CuffSert-formatted metadata from an existing stack.'
+      opts.separator('')
+      opts.separator('Usage: cuffdown stack-name')
+      CuffBase.shared_cli_args(opts, args)
+    end
+    stackname, _ = parser.parse(argv)
+    args[:stackname] = stackname
+    args
+  end
+
+  def self.parameters(stack)
+    (stack[:parameters] || []).map do |param|
+      {
+        'Name' => param[:parameter_key],
+        'Value' => param[:parameter_value],
+      }
+    end
+  end
+
+  def self.tags(stack)
+    (stack[:tags] || []).map do |param|
+      {
+        'Name' => param[:key],
+        'Value' => param[:value],
+      }
+    end
+  end
+
+  def self.dump(name, params, tags, output)
+    result = {
+      'Format' => 'v1',
+      'Suffix' => name,
+      'Parameters' => params,
+      'Tags' => tags,
+    }
+    YAML.dump(result, output)
+  end
+
+  def self.run(argv, output)
+    cli_args = self.parse_cli_args(argv)
+    meta = CuffSert::StackConfig.new
+    meta.stackname = cli_args[:stackname]
+    client = CuffSert::RxCFClient.new(cli_args[:aws_region])
+    stack = client.find_stack_blocking(meta)
+    unless stack
+      STDERR.puts "No such stack #{meta.stackname}"
+      exit(1)
+    end
+    stack = stack.to_h
+    self.dump(
+      stack[:stack_name],
+      self.parameters(stack),
+      self.tags(stack),
+      output
+    )
+  end
+end
diff --git a/lib/cuffsert/cli_args.rb b/lib/cuffsert/cli_args.rb
index 939f439..e20cfcd 100644
--- a/lib/cuffsert/cli_args.rb
+++ b/lib/cuffsert/cli_args.rb
@@ -1,4 +1,5 @@
 require 'optparse'
+require 'cuffbase'
 require 'cuffsert/version'
 
 module CuffSert
@@ -23,6 +24,9 @@ def self.parse_cli_args(argv)
       opts.separator('  cuffsert --name <stackname> {--parameter Name=Value | --tag Name=Value}... [stack.json]')
       opts.separator('  cuffsert --metadata <metadata.json> --selector <path/in/metadata> stack.json')
       opts.separator('  cuffsert --metadata <metadata.json> --selector <path/in/metadata> {--parameter Name=Value | --tag Name=Value}... [stack.json]')
+
+      CuffBase.shared_cli_args(opts, args)
+
       opts.on('--metadata path', '-m path', 'Yaml file to read stack metadata from') do |path|
         path = '/dev/stdin' if path == '-'
         unless File.exist?(path)
@@ -64,10 +68,6 @@ def self.parse_cli_args(argv)
         args[:overrides][:tags][key] = val
       end
 
-      opts.on('--region=aws_region', 'AWS region, overrides env variable AWS_REGION') do |region|
-        args[:aws_region] = region
-      end
-
       opts.on('--s3-upload-prefix=prefix', 'Templates > 51200 bytes are uploaded here. Format: s3://bucket-name/[pre/fix]') do |prefix|
         unless prefix.start_with?('s3://')
           raise "Upload prefix #{prefix} must start with s3://"
diff --git a/spec/cuffdown/main_spec.rb b/spec/cuffdown/main_spec.rb
new file mode 100644
index 0000000..cb01813
--- /dev/null
+++ b/spec/cuffdown/main_spec.rb
@@ -0,0 +1,38 @@
+require 'cuffdown/main'
+require 'spec_helpers'
+
+describe CuffDown do
+  include_context 'stack states'
+
+  describe '.run' do
+    let(:cli_args) { ['some-stack'] }
+    let(:output) { StringIO.new }
+    let :stack_complete do
+      super().merge(
+        :parameters => [
+          {:parameter_key => 'p1', :parameter_value => 'v1'}
+        ]
+      )
+    end
+
+    let(:cfmock) { double(:cfmock) }
+
+    before do
+      allow(Aws::CloudFormation::Client).to receive(:new).and_return(cfmock)
+      allow(cfmock).to receive(:describe_stacks).and_return(stack_complete_describe)
+      CuffDown.run(cli_args, output)
+    end
+
+    it 'outputs parameter values for the stack' do
+      expect(output.string).to match(/Name: p1.*Value: v1/m)
+    end
+
+    context 'when invoked with an explicit region' do
+      let(:cli_args) { ['--region', 'rp-north-1', 'stack-name'] }
+
+      it 'passes region to the ClodFormation client' do
+        expect(Aws::CloudFormation::Client).to have_received(:new).with(hash_including(:region => 'rp-north-1'))
+      end
+    end
+  end
+end