Add assert_threads_result helper and threads test

Author: st0012

test/protocol/threads_test.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require_relative '../support/test_case'
+
+module DEBUGGER__
+  class ThreadsTest < TestCase
+    PROGRAM = <<~RUBY
+       1| def foo
+       2|   Thread.new { sleep 30 }
+       3| end
+       4|
+       5| foo
+       6| sleep 0.1 # make sure the thread stops
+       7| binding.b
+    RUBY
+
+    def test_reponse_returns_correct_threads_info
+      run_protocol_scenario PROGRAM do
+        req_continue
+
+        assert_threads_result(
+          [
+            /\.rb:6:in `<main>'/,
+            /\.rb:2:in `block in foo'/
+          ]
+        )
+
+        req_terminate_debuggee
+      end
+    end
+  end
+end
+

test/support/protocol_utils.rb

@@ -268,6 +268,24 @@ def assert_locals_result expected, frame_idx: 0
       end
     end
 
+    def assert_threads_result(expected_names)
+      case ENV['RUBY_DEBUG_TEST_UI']
+      when 'vscode'
+        send_request 'threads'
+        res = find_crt_dap_response
+        assert_dap_response :ThreadsResponse, res
+
+        threads = res.dig(:body, :threads)
+        failure_msg = FailureMessage.new{create_protocol_message "result:\n#{JSON.pretty_generate res}"}
+
+        assert_equal expected_names.count, threads.count, failure_msg
+
+        expected_names.each_with_index do |expected, index|
+          assert_match expected, threads[index][:name], failure_msg
+        end
+      end
+    end
+
     def assert_hover_result expected,  expression: nil, frame_idx: 0
       case ENV['RUBY_DEBUG_TEST_UI']
       when 'vscode'