Add a pack option to the builder options

test/configuration/builder_test.rb

@@ -32,6 +32,24 @@ class ConfigurationBuilderTest < ActiveSupport::TestCase
     assert_equal false, config.builder.remote?
   end
 
+  test "pack?" do
+    refute config.builder.pack?
+  end
+
+  test "pack? with pack builder" do
+    @deploy[:builder] = { "pack" => {"builder" => "heroku/builder:24"} }
+
+    assert config.builder.pack?
+  end
+
+  test "pack details" do
+    @deploy[:builder] = { "pack" => {"arch" => "amd64", "builder" => "heroku/builder:24", "buildpacks" => ["heroku/ruby", "heroku/procfile"]} }
+
+    assert_equal "amd64", config.builder.pack_arch
+    assert_equal "heroku/builder:24", config.builder.pack_builder
+    assert_equal ["heroku/ruby", "heroku/procfile"], config.builder.pack_buildpacks
+  end
+
   test "remote_arch" do
     assert_nil config.builder.remote_arch
   end