Protect against stale reads in specs

spec/elevate_spec.rb

@@ -2,7 +2,7 @@ class TestController
   include Elevate
 
   def initialize
-    @invocations = {}
+    @invocations = ThreadsafeProxy.new({})
     @counter = 0
     @threads = []
     @updates = []

spec/support/threadsafe_proxy.rb

@@ -0,0 +1,18 @@
+class ThreadsafeProxy
+  def initialize(target)
+    @mutex = Mutex.new
+    @target = target
+  end
+
+  def method_missing(m, *args, &block)
+    @mutex.synchronize do
+      @target.__send__(m, *args, &block)
+    end
+  end
+
+  def respond_to_missing?(m, include_private = false)
+    @mutex.synchronize do
+      @target.respond_to_missing?(m, include_private)
+    end
+  end
+end