[tests] Fix threading issue with parallel testing with non-threadsafe rspec mocks

Author: chadlwilson

src/spec/ruby/rack/application_spec.rb

@@ -792,7 +792,11 @@ def createRackServletWrapper(runtime, rackup, filename)
     expect(millis).to be >= 90 # waited about ~ 0.10 secs
   end
 
-  it "initializes initial runtimes in paralel (with wait set to false)" do
+  it "initializes initial runtimes in parallel (with wait set to false)" do
+    @factory = double("factory (non-tracking)", null_object: true)
+    @pooling_factory = org.jruby.rack.PoolingRackApplicationFactory.new @factory
+    @pooling_factory.context = @rack_context
+
     allow(@factory).to receive(:init)
     allow(@factory).to receive(:newApplication) do
       app = double "app"