extract the buildpack into its own image

Dockerfile

+FROM heroku/cedar:14
+
+RUN useradd -d /app -m app
+USER app
+
+WORKDIR /buildpack
+COPY bin/ /buildpack/bin/
+COPY scripts/ /buildpack/scripts/
+RUN /buildpack/bin/compile /app
+
+ENV HOME /app
+ENV PORT 3000
+EXPOSE 3000
+
+ONBUILD WORKDIR /app/
+ONBUILD COPY . /app/
+ONBUILD CMD /app/bin/boot

spec/fixtures/hello_world/Dockerfile

-FROM heroku/cedar:14
-
-RUN useradd -d /app -m app
-USER app
-WORKDIR /app
-
-ENV HOME /app
-ENV PORT 3000
-
-RUN mkdir -p /app
-COPY . /app/
-
-RUN /app/buildpack/bin/compile /app
-
-EXPOSE 3000
-CMD /app/bin/boot
+FROM hone/static:14

spec/simple_spec.rb

 require_relative "spec_helper"
-require_relative "support/buildpack_runner"
+require_relative "support/app_runner"
+require_relative "support/buildpack_builder"
 
 describe "Simple" do
-  let(:bp) { BuildpackRunner.new("hello_world") }
+  let(:debug) { false }
+  let(:app)   { AppRunner.new("hello_world", debug) }
+  before      { BuildpackBuilder.new(debug) }
 
   after do
-    bp.destroy
+    app.destroy
   end
 
   it "should serve out of public_html by default" do
-    response = bp.get("/")
+    response = app.get("/")
     expect(response.code).to eq("200")
     expect(response.body.chomp).to eq("Hello World")
   end

spec/support/buildpack_runner.rb → spec/support/app_runner.rb

@@ -5,7 +5,7 @@ require "json"
 require "docker"
 require_relative "path_helper"
 
-class BuildpackRunner
+class AppRunner
   include PathHelper
 
   HOST_PORT      = "3000"
@@ -15,14 +15,13 @@ class BuildpackRunner
   def initialize(fixture, debug = false)
     @debug     = debug
     @image     = build_image(fixture)
-    puts @image.id if @debug
     @container = Docker::Container.create(
       'Image'      => @image.id,
       'HostConfig' => {
         'PortBindings' => {
           "#{CONTAINER_PORT}/tcp" => [{
             "HostIp" => HOST_IP,
-            "HostPort": HOST_PORT, 
+            "HostPort": HOST_PORT,
           }]
         }
       }
@@ -59,8 +58,6 @@ class BuildpackRunner
     image = nil
 
     Dir.mktmpdir do |tmpdir|
-      fixture_path = fixtures_path(fixture)
-      dest_bp_dir  = Pathname.new(File.join(tmpdir, "buildpack"))
       print_output =
         if @debug
           -> (chunk) {
@@ -71,11 +68,8 @@ class BuildpackRunner
           -> (chunk) { nil }
         end
 
-      FileUtils.mkdir_p(dest_bp_dir)
-      FileUtils.cp_r(buildpack_path("bin"), dest_bp_dir)
-      FileUtils.cp_r(buildpack_path("scripts"), dest_bp_dir)
-      FileUtils.cp_r(Dir.glob(fixture_path + "*"), tmpdir)
-      image = Docker::Image.build_from_dir(tmpdir, &print_output)
+      FileUtils.cp_r(Dir.glob(fixtures_path(fixture) + "*"), tmpdir)
+      image = Docker::Image.build_from_dir(tmpdir, 'rm' => true, &print_output)
     end
 
     image

spec/support/buildpack_builder.rb

+require "tmpdir"
+require "fileutils"
+require "docker"
+require_relative "path_helper"
+
+class BuildpackBuilder
+  include PathHelper
+
+  TAG = "hone/static:14"
+
+  def initialize(debug = false)
+    @debug = debug
+    @image = build_image
+  end
+
+  def build_image
+    print_output =
+      if @debug
+        -> (chunk) {
+          json = JSON.parse(chunk)
+          puts json["stream"]
+        }
+      else
+        -> (chunk) { nil }
+      end
+
+    Docker::Image.build_from_dir(buildpack_path.to_s, 't' => TAG, 'rm' => true, &print_output)
+  end
+end