Let firefox choose the bidi port by default

rb/lib/selenium/webdriver/firefox/service.rb

@@ -28,9 +28,9 @@ class Service < WebDriver::Service
 
         def initialize(path: nil, port: nil, log: nil, args: nil)
           args ||= []
-          unless args.any? { |arg| arg.include?('--connect-existing') }
+          unless args.any? { |arg| arg.include?('--connect-existing') || arg.include?('--websocket-port') }
             args << '--websocket-port'
-            args << WebDriver::PortProber.above(9222).to_s
+            args << '0'
           end
           super
         end

rb/spec/integration/selenium/webdriver/firefox/service_spec.rb

@@ -39,21 +39,6 @@ module Firefox
         it 'can be started outside driver' do
           expect(service_manager.uri).to be_a(URI)
         end
-
-        context 'with BiDi enabled', exclusive: {bidi: true, reason: 'only executed when bidi is enabled'} do
-          it 'ensures two service instances use different websocket port' do
-            service1 = described_class.new
-            service2 = described_class.new
-
-            ws_index1 = service1.args.index('--websocket-port')
-            ws_index2 = service2.args.index('--websocket-port')
-
-            port1 = service1.args[ws_index1 + 1].to_i
-            port2 = service2.args[ws_index2 + 1].to_i
-
-            expect(port1).not_to eq(port2)
-          end
-        end
       end
     end # Firefox
   end # WebDriver

rb/spec/unit/selenium/webdriver/firefox/service_spec.rb

@@ -77,11 +77,11 @@ module Firefox
             expect(service.extra_args).to include(*%w[--foo --bar])
           end
 
-          it 'there is a random port for websocket' do
+          it 'there is a zero port for websocket' do
             service = described_class.new
             ws_index = service.extra_args.index('--websocket-port')
             port = service.extra_args[ws_index + 1].to_i
-            expect(port).to be_positive
+            expect(port).to be_zero
           end
 
           context 'with connect existing' do
@@ -91,6 +91,14 @@ module Firefox
               expect(service.extra_args).to eq(['--connect-existing'])
             end
           end
+
+          context 'with websocket port' do
+            it 'does not add websocket-port' do
+              service = described_class.new(args: ['--websocket-port=1234'])
+              expect(service.extra_args).not_to include('--websocket-port=0')
+              expect(service.extra_args).to eq(['--websocket-port=1234'])
+            end
+          end
         end
 
         context 'when initializing driver' do