diff --git a/collects/rackunit/private/gui/controller.rkt b/collects/rackunit/private/gui/controller.rkt
index 16ba57fd0f..9d45086d39 100644
--- a/collects/rackunit/private/gui/controller.rkt
+++ b/collects/rackunit/private/gui/controller.rkt
@@ -16,13 +16,18 @@
     ;; The model currently displayed in the Details view, of #f is none.
     (define-notify selected-model (new notify-box% (value #f)))
 
+    ;; locked? : (notify-box boolean)
+    (define-notify locked? (new notify-box% (value #f)))
+
     ;; view : #f or view<%>
     (define view #f)
 
     ;; check-ready : -> void
     (define/private (check-ready)
       (unless view
-        (error 'racunit "The RacUnit GUI is no longer running.")))
+        (error 'racunit "The RacUnit GUI is no longer running."))
+      (when (get-locked?)
+        (error 'racunit "The RacUnit GUI is locked and not accepting tests.")))
 
     ;; create-model : test suite<%>/#f -> result<%>
     (define/public (create-model test parent)
@@ -47,7 +52,7 @@
 
     ;; on-model-status-change : model<%> -> void
     (define/public (on-model-status-change model)
-      (check-ready)
+      ;; (check-ready) ;; allow completion of tests to change status
       (send view queue-for-update model)
       (let [(parent (send model get-parent))]
         (when parent (send parent on-child-status-change model))))
diff --git a/collects/rackunit/private/gui/interfaces.rkt b/collects/rackunit/private/gui/interfaces.rkt
index 004a08628f..adcff8f9d5 100644
--- a/collects/rackunit/private/gui/interfaces.rkt
+++ b/collects/rackunit/private/gui/interfaces.rkt
@@ -14,7 +14,10 @@
    create-model
    on-model-status-change
    register-view
-   on-view-shutdown))
+   on-view-shutdown
+
+   ;; field: locked?
+   ))
 
 ;; result
 ;; Represents a test (case or suite) together with the state associated
diff --git a/collects/rackunit/private/gui/view.rkt b/collects/rackunit/private/gui/view.rkt
index c966a7c173..84aec27b81 100644
--- a/collects/rackunit/private/gui/view.rkt
+++ b/collects/rackunit/private/gui/view.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 (require racket/class
          unstable/class-iop
+         unstable/gui/notify
          racket/list
          racket/gui
          framework
@@ -276,6 +277,7 @@ still be there, just not visible?
     (inherit get-help-menu
              get-width
              get-height
+             get-menu-bar
              get-area-container)
 
     (define-syntax override-false
@@ -306,6 +308,14 @@ still be there, just not visible?
 
     (super-new (width width) (height height))
     (send (get-help-menu) delete)
+    (let ([racunit-menu
+           (new menu%
+                (label "RacUnit")
+                (parent (get-menu-bar)))])
+      (menu-option/notify-box racunit-menu
+                              "Lock"
+                              (get-field locked? controller)))
+
     (define view
       (new view%
            (controller controller)