diff --git a/java/debugger/impl/src/com/intellij/debugger/engine/DebuggerManagerThreadImpl.java b/java/debugger/impl/src/com/intellij/debugger/engine/DebuggerManagerThreadImpl.java
index 416d63e8f8ae..fe18a899ee48 100644
--- a/java/debugger/impl/src/com/intellij/debugger/engine/DebuggerManagerThreadImpl.java
+++ b/java/debugger/impl/src/com/intellij/debugger/engine/DebuggerManagerThreadImpl.java
@@ -29,6 +29,7 @@ import com.intellij.openapi.progress.util.ProgressWindowWithNotification;
 import com.intellij.util.Alarm;
 import com.sun.jdi.VMDisconnectedException;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.TestOnly;
 
 /**
  * @author lex
@@ -43,6 +44,7 @@ public class DebuggerManagerThreadImpl extends InvokeAndWaitThread<DebuggerComma
     super();
   }
 
+  @TestOnly
   public static DebuggerManagerThreadImpl createTestInstance() {
     return new DebuggerManagerThreadImpl();
   }
@@ -222,4 +224,10 @@ public class DebuggerManagerThreadImpl extends InvokeAndWaitThread<DebuggerComma
     }
 
   }
+
+  @TestOnly
+  public void clearQueue() {
+    myEvents.clearQueue();
+  }
+
 }
diff --git a/java/debugger/impl/src/com/intellij/debugger/impl/EventQueue.java b/java/debugger/impl/src/com/intellij/debugger/impl/EventQueue.java
index df2c11c46da6..f03dae6eb841 100644
--- a/java/debugger/impl/src/com/intellij/debugger/impl/EventQueue.java
+++ b/java/debugger/impl/src/com/intellij/debugger/impl/EventQueue.java
@@ -17,6 +17,7 @@ package com.intellij.debugger.impl;
 
 import com.intellij.openapi.diagnostic.Logger;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.TestOnly;
 
 import java.util.LinkedList;
 import java.util.concurrent.locks.Condition;
@@ -50,6 +51,7 @@ public class EventQueue<E> {
 
     myLock.lock();
     try {
+      assertOpen();
       getEventsList(priority).addFirst(event);
       myEventsAvailable.signalAll();
     }
@@ -65,6 +67,7 @@ public class EventQueue<E> {
 
     myLock.lock();
     try {
+      assertOpen();
       getEventsList(priority).offer(event);
       myEventsAvailable.signalAll();
     }
@@ -80,6 +83,7 @@ public class EventQueue<E> {
   public void close(){
     myLock.lock();
     try {
+      assertOpen();
       myIsClosed = true;
       myEventsAvailable.signalAll();
     }
@@ -88,6 +92,10 @@ public class EventQueue<E> {
     }
   }
 
+  private void assertOpen() {
+    if (myIsClosed) throw new AssertionError("Already closed");
+  }
+
   private E getEvent() throws EventQueueClosedException {
     myLock.lock();
     try {
@@ -120,4 +128,12 @@ public class EventQueue<E> {
   public E getCurrentEvent() {
     return myCurrentEvent;
   }
+
+  @TestOnly
+  public void clearQueue() {
+    myCurrentEvent = null;
+    for (LinkedList event : myEvents) {
+      event.clear();
+    }
+  }
 }