Add simplecov (#760)

.gitignore

@@ -53,3 +53,5 @@ compose-dev.yaml
 
 # Ignore GCP keyfile
 gcp-storage-keyfile.json
+
+coverage

Gemfile

@@ -71,4 +71,5 @@ group :test do
   gem "vcr"
   gem "webmock"
   gem "climate_control"
+  gem "simplecov", require: false
 end

Gemfile.lock

@@ -171,6 +171,7 @@ GEM
     debug (1.9.2)
       irb (~> 1.10)
       reline (>= 0.3.8)
+    docile (1.4.0)
     dotenv (3.1.2)
     dotenv-rails (3.1.2)
       dotenv (= 3.1.2)
@@ -399,6 +400,12 @@ GEM
     sentry-ruby (5.17.3)
       bigdecimal
       concurrent-ruby (~> 1.0, >= 1.0.2)
+    simplecov (0.22.0)
+      docile (~> 1.1)
+      simplecov-html (~> 0.11)
+      simplecov_json_formatter (~> 0.1)
+    simplecov-html (0.12.3)
+    simplecov_json_formatter (0.1.4)
     smart_properties (1.17.0)
     sorbet-runtime (0.5.11383)
     stackprof (0.2.26)
@@ -493,6 +500,7 @@ DEPENDENCIES
   selenium-webdriver
   sentry-rails
   sentry-ruby
+  simplecov
   stackprof
   stimulus-rails
   tailwindcss-rails

test/test_helper.rb

@@ -1,3 +1,10 @@
+if ENV["COVERAGE"]
+  require "simplecov"
+  SimpleCov.start "rails" do
+    enable_coverage :branch
+  end
+end
+
 # Test ENV setup:
 # By default, all features should be disabled
 # Use the `with_env_overrides` helper to enable features for individual tests
@@ -28,6 +35,17 @@ module ActiveSupport
     # Run tests in parallel with specified workers
     parallelize(workers: :number_of_processors)
 
+    # https://github.com/simplecov-ruby/simplecov/issues/718#issuecomment-538201587
+    if ENV["COVERAGE"]
+      parallelize_setup do |worker|
+        SimpleCov.command_name "#{SimpleCov.command_name}-#{worker}"
+      end
+
+      parallelize_teardown do |worker|
+        SimpleCov.result
+      end
+    end
+
     # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
     fixtures :all