diff --git a/Gemfile b/Gemfile
index 1c0be7266..8fcd22e75 100644
--- a/Gemfile
+++ b/Gemfile
@@ -314,4 +314,7 @@ group :development, :test do
   gem "jasmine-jquery-rails",      "2.0.3"
   gem "rails-assets-jasmine-ajax", "3.3.1", source: "https://rails-assets.org"
   gem "sinon-rails",               "1.15.0"
+
+  # For `assigns` in controller specs
+  gem "rails-controller-testing", "1.0.2"
 end
diff --git a/Gemfile.lock b/Gemfile.lock
index 193edc8f7..5ed511fe9 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -550,6 +550,10 @@ GEM
     rails-assets-markdown-it-sup (1.0.0)
     rails-assets-perfect-scrollbar (0.6.16)
     rails-assets-underscore (1.8.3)
+    rails-controller-testing (1.0.2)
+      actionpack (~> 5.x, >= 5.0.1)
+      actionview (~> 5.x, >= 5.0.1)
+      activesupport (~> 5.x)
     rails-dom-testing (2.0.3)
       activesupport (>= 4.2.0)
       nokogiri (>= 1.6)
@@ -860,6 +864,7 @@ DEPENDENCIES
   rails-assets-markdown-it-sub (= 1.0.0)!
   rails-assets-markdown-it-sup (= 1.0.0)!
   rails-assets-perfect-scrollbar (= 0.6.16)!
+  rails-controller-testing (= 1.0.2)
   rails-i18n (= 5.0.4)
   rails-timeago (= 2.16.0)
   rb-fsevent (= 0.10.2)