fix(tests): 修复 SimulatedXRaySourceTests 因 VariablesConnectedEvent 未被 Mock 导致的失败

SimulatedXRaySource.ConnectVariables() 中新增的 VariablesConnectedEvent
发布未被测试的 EventAggregator Mock 覆盖，导致 GetEvent<T>() 返回 null，
触发 NullReferenceException，5 个测试全部失败。

- 补充 VariablesConnectedEvent、StatusUpdatedEvent 的 Mock 设置
- Initialize_SetsInitializedTrue 增加 VariablesConnectedEvent(true) 发布断言
- 修正 TurnOff_PublishesClosedEvent 断言逻辑：Arrange 阶段
  ConnectVariables/TurnOn 已产生一次 Closed 事件，需在 Act 前清空
  Invocations 避免误判发布次数

XplorePlane.Tests/Hardware/SimulatedXRaySourceTests.cs

@@ -13,6 +13,8 @@ namespace XplorePlane.Tests.Hardware
         private readonly Mock<IEventAggregator> _mockEventAggregator;
         private readonly Mock<ILoggerService> _mockLogger;
         private readonly Mock<RaySourceStatusChangedEvent> _mockStatusEvent;
+        private readonly Mock<VariablesConnectedEvent> _mockVariablesConnectedEvent;
+        private readonly Mock<StatusUpdatedEvent> _mockStatusUpdatedEvent;
         private readonly SimulatedXRaySource _source;
 
         public SimulatedXRaySourceTests()
@@ -20,6 +22,8 @@ namespace XplorePlane.Tests.Hardware
             _mockEventAggregator = new Mock<IEventAggregator>();
             _mockLogger = new Mock<ILoggerService>();
             _mockStatusEvent = new Mock<RaySourceStatusChangedEvent>();
+            _mockVariablesConnectedEvent = new Mock<VariablesConnectedEvent>();
+            _mockStatusUpdatedEvent = new Mock<StatusUpdatedEvent>();
 
             // Setup logger to return itself for ForModule<T>()
             _mockLogger.Setup(l => l.ForModule<SimulatedXRaySource>()).Returns(_mockLogger.Object);
@@ -29,6 +33,18 @@ namespace XplorePlane.Tests.Hardware
                 .Setup(ea => ea.GetEvent<RaySourceStatusChangedEvent>())
                 .Returns(_mockStatusEvent.Object);
 
+            // ConnectVariables() 会发布 VariablesConnectedEvent，需要 Mock 该事件避免 NullReferenceException
+            // ConnectVariables() publishes VariablesConnectedEvent, must mock it to avoid NullReferenceException
+            _mockEventAggregator
+                .Setup(ea => ea.GetEvent<VariablesConnectedEvent>())
+                .Returns(_mockVariablesConnectedEvent.Object);
+
+            // TurnOn/TurnOff/SetVoltage/SetCurrent 会发布 StatusUpdatedEvent，同样需要 Mock
+            // TurnOn/TurnOff/SetVoltage/SetCurrent publish StatusUpdatedEvent, also needs mocking
+            _mockEventAggregator
+                .Setup(ea => ea.GetEvent<StatusUpdatedEvent>())
+                .Returns(_mockStatusUpdatedEvent.Object);
+
             _source = new SimulatedXRaySource(_mockEventAggregator.Object, _mockLogger.Object);
         }
 
@@ -43,6 +59,10 @@ namespace XplorePlane.Tests.Hardware
             Assert.True(initResult.Success);
             Assert.True(connectResult.Success);
             Assert.True(_source.IsConnected);
+
+            // 验证 ConnectVariables 发布了 VariablesConnectedEvent(true)
+            // Verify ConnectVariables published VariablesConnectedEvent(true)
+            _mockVariablesConnectedEvent.Verify(e => e.Publish(true), Times.Once);
         }
 
         [Fact]
@@ -70,6 +90,11 @@ namespace XplorePlane.Tests.Hardware
             _source.ConnectVariables();
             _source.TurnOn();
 
+            // ConnectVariables/TurnOn 阶段已经发布过 Closed/Opened 事件，清空调用记录避免影响 Act 阶段的断言
+            // ConnectVariables/TurnOn already published Closed/Opened events during Arrange; clear invocations
+            // so the Act-phase assertion only counts the publish triggered by TurnOff()
+            _mockStatusEvent.Invocations.Clear();
+
             // Act
             var result = _source.TurnOff();