Compile Webpacker assets only once in test environment

config/webpacker.yml

@@ -71,15 +71,7 @@ development:
     watch_options:
       ignored: '**/node_modules/**'
 
-
-test:
-  <<: *default
-  compile: true
-
-  # Compile test packs to a separate directory
-  public_output_path: packs-test
-
-production:
+production: &production
   <<: *default
 
   # Production depends on precompilation of packs prior to booting for performance.
@@ -90,3 +82,9 @@ production:
 
   # Cache manifest.json for performance
   cache_manifest: true
+
+test:
+  <<: *production
+
+  # Compile test packs to a separate directory
+  public_output_path: packs-test

spec/spec_helper.rb

@@ -55,6 +55,12 @@ RSpec.configure do |config|
     Capybara.reset_sessions!
   end
 
+  # Precompile Webpacker assets (once) when starting the suite. The default setup can result
+  # in the assets getting compiled many times throughout the build, slowing it down.
+  config.before :suite do
+    Webpacker.compile
+  end
+
   # Fix encoding issue in Rails 5.0; allows passing empty arrays or hashes as params.
   config.before(:each, type: :controller) { @request.env["CONTENT_TYPE"] = 'application/json' }