Add test helper methods from Rails add-on (#2991)

* Add test helper methods from Rails add-on

.rubocop.yml

@@ -60,6 +60,7 @@ Sorbet/StrictSigil:
     - "lib/ruby_indexer/lib/ruby_indexer/prefix_tree.rb"
     - "lib/ruby_lsp/load_sorbet.rb"
     - "lib/ruby_lsp/scripts/compose_bundle.rb"
+    - "lib/ruby_lsp/test_helper.rb"
 
 Layout/ClassStructure:
   Enabled: true

lib/ruby_lsp/test_helper.rb

@@ -1,11 +1,16 @@
-# typed: strict
+# typed: true
 # frozen_string_literal: true
 
 # NOTE: This module is intended to be used by addons for writing their own tests, so keep that in mind if changing.
 
 module RubyLsp
   module TestHelper
+    class TestError < StandardError; end
+
     extend T::Sig
+    extend T::Helpers
+
+    requires_ancestor { Kernel }
 
     sig do
       type_parameters(:T)
@@ -52,5 +57,33 @@ def with_server(source = nil, uri = Kernel.URI("file:///fake.rb"), stub_no_typec
         server.run_shutdown
       end
     end
+
+    sig { params(server: RubyLsp::Server).returns(RubyLsp::Result) }
+    def pop_result(server)
+      result = server.pop_response
+      result = server.pop_response until result.is_a?(RubyLsp::Result) || result.is_a?(RubyLsp::Error)
+
+      if result.is_a?(RubyLsp::Error)
+        raise TestError, "Failed to execute request #{result.message}"
+      else
+        result
+      end
+    end
+
+    def pop_log_notification(message_queue, type)
+      log = message_queue.pop
+      return log if log.params.type == type
+
+      log = message_queue.pop until log.params.type == type
+      log
+    end
+
+    def pop_message(outgoing_queue, &block)
+      message = outgoing_queue.pop
+      return message if block.call(message)
+
+      message = outgoing_queue.pop until block.call(message)
+      message
+    end
   end
 end