Wait for activation under a mutex lock

Author: vinistock

test/test_helper.rb

@@ -32,16 +32,23 @@ class TestCase
     extend T::Sig
     include RubyLsp::TestHelper
 
+    def before_setup
+      super
+      @mutex = Mutex.new
+    end
+
     sig { returns(String) }
     def dummy_root
       File.expand_path("#{__dir__}/dummy")
     end
 
     sig { void }
     def wait_for_rails_addon_activation
-      Thread.new do
-        T.cast(RubyLsp::Addon.addons.first, RubyLsp::Rails::Addon).rails_runner_client
-      end.join
+      @mutex.synchronize do
+        Thread.new do
+          T.cast(RubyLsp::Addon.addons.first, RubyLsp::Rails::Addon).rails_runner_client
+        end.join
+      end
     end
 
     sig { params(server: RubyLsp::Server).returns(RubyLsp::Result) }