Instantiate and assign a Layout in the Runner

lib/uh/wm/runner.rb

@@ -10,12 +10,14 @@ module Uh
         end
       end
 
-      attr_reader :env, :events, :manager
+      attr_reader :env, :events, :manager, :layout
 
       def initialize env, manager: nil, stopped: false
+        raise ArgumentError, 'missing env layout class' unless env.layout_class
         @env      = env
         @events   = Dispatcher.new
         @manager  = manager || Manager.new(@events)
+        @layout   = @env.layout_class.new
         @stopped  = stopped
       end
 

spec/uh/wm/runner_spec.rb

@@ -1,7 +1,11 @@
+SomeLayout = Class.new
+
 module Uh
   module WM
     RSpec.describe Runner do
-      let(:env)         { Env.new(StringIO.new) }
+      let(:env) do
+        Env.new(StringIO.new).tap { |o| o.layout_class = SomeLayout }
+      end
       subject(:runner) { described_class.new env }
 
       describe '.run' do
@@ -49,6 +53,17 @@ module Uh
         it 'is not stopped' do
           expect(runner).not_to be_stopped
         end
+
+        it 'assigns a new layout instance' do
+          expect(runner.layout).to be_an_instance_of SomeLayout
+        end
+
+        context 'when the env has no layout set' do
+          before { env.layout_class = nil }
+          it 'raises an ArgumentError' do
+            expect { runner }.to raise_error WM::ArgumentError
+          end
+        end
       end
 
       describe '#stopped?' do