Precompile assets before tests in test.rb so we get it early enough, …

…and working for all tests

config/environments/test.rb

@@ -13,11 +13,14 @@
 
   # Simulate same asset settings as production
   # This requires us to run yarn build, yarn build:css and rails assets:precompile before running tests
-  # This should be automatically done if you are running specs through parallel_spec or spec in rake
+  # This should be automatically done for you.
   config.assets.prefix = "/assets-test"
   config.assets.compile = false
   config.serve_static_files = true
 
+  # Run precompilation before tests are run
+  system("rake precompile_assets_once")
+
   # Settings specified here will take precedence over those in config/application.rb.
 
   config.cache_classes = false

lib/tasks/precompile_assets_before_spec.rake → lib/tasks/precompile_assets_before_parallel_spec.rake

@@ -5,9 +5,8 @@ def precompile_assets_before(task_name)
 
   task = Rake::Task[task_name]
 
-  task.enhance(["assets:precompile"])
+  task.enhance(["precompile_assets_once"])
 end
 
-# Enhance both spec and parallel:spec to precompile assets and clobber them after, to simulate prod
-precompile_assets_before "spec"
+# Enhance parallel:spec to precompile assets once, so it won't run per process
 precompile_assets_before "parallel:spec"

lib/tasks/precompile_assets_once.rake

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+task "precompile_assets_once" => :environment do
+  next if ENV["TEST_ASSET_PRECOMPILE_DONE"]
+
+  p "Compiling assets..."
+  ENV["TEST_ASSET_PRECOMPILE_DONE"] = "true"
+  compilation = Rake::Task["assets:precompile"].invoke
+
+  abort "Pre-compilation failed. Cannot run tests." unless compilation
+
+  p "Assets compiled"
+end