diff --git a/spec/controllers/execution_environments_controller_spec.rb b/spec/controllers/execution_environments_controller_spec.rb
index 6a6b4b64..db22403c 100644
--- a/spec/controllers/execution_environments_controller_spec.rb
+++ b/spec/controllers/execution_environments_controller_spec.rb
@@ -92,7 +92,19 @@ describe ExecutionEnvironmentsController do
     expect_template(:new)
   end
 
-  describe '#set_docker_images', docker: true do
+  describe '#set_docker_images' do
+    context 'when Docker is available' do
+      let(:docker_images) { [1, 2, 3] }
+
+      before(:each) do
+        expect(DockerClient).to receive(:check_availability!).at_least(:once)
+        expect(DockerClient).to receive(:image_tags).and_return(docker_images)
+        controller.send(:set_docker_images)
+      end
+
+      expect_assigns(docker_images: :docker_images)
+    end
+
     context 'when Docker is unavailable' do
       let(:error_message) { 'Docker is unavailable' }
 
diff --git a/spec/helpers/application_helper_spec.rb b/spec/helpers/application_helper_spec.rb
index 1c891070..5786927c 100644
--- a/spec/helpers/application_helper_spec.rb
+++ b/spec/helpers/application_helper_spec.rb
@@ -35,6 +35,23 @@ describe ApplicationHelper do
     end
   end
 
+  describe '#progress_bar' do
+    let(:html) { progress_bar(value) }
+    let(:value) { 42 }
+
+    it "builds nested 'div' tags" do
+      expect(html).to have_css('div.progress div.progress-bar')
+    end
+
+    it 'assigns the correct text' do
+      expect(html).to have_text("#{value}%")
+    end
+
+    it 'uses the correct width' do
+      expect(html).to have_css("div.progress-bar[style='width: 42%;']")
+    end
+  end
+
   describe '#row' do
     let(:html) { row(label: 'foo', value: 42) }
 
diff --git a/spec/support/controllers.rb b/spec/support/controllers.rb
index cc9a5dd9..6081ab2e 100644
--- a/spec/support/controllers.rb
+++ b/spec/support/controllers.rb
@@ -1,10 +1,10 @@
 def expect_assigns(pairs)
-  pairs.each_pair do |key, value|
+  pairs.each do |key, value|
     it "assigns @#{key}" do
       if value.is_a?(Class)
         expect(assigns(key)).to be_a(value)
       else
-        object = value.is_a?(Symbol) ? send(value) : value
+        object = obtain_object(value)
         if object.is_a?(ActiveRecord::Relation) || object.is_a?(Array)
           expect(assigns(key)).to match_array(object)
         else
@@ -54,3 +54,14 @@ def expect_template(template)
     expect(controller).to render_template(template)
   end
 end
+
+def obtain_object(value)
+  case value
+  when Proc
+    value.call
+  when Symbol
+    send(value)
+  else
+    value
+  end
+end