From 77b0482febced944fba0104b3b2431773414fccf Mon Sep 17 00:00:00 2001
From: Brandon Keepers <brandon@collectiveidea.com>
Date: Sun, 5 Sep 2010 17:06:44 -0400
Subject: [PATCH] Only set backend if one is not already set

---
 lib/delayed/worker.rb |  2 +-
 spec/worker_spec.rb   | 20 +++++++++++++++++++-
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/lib/delayed/worker.rb b/lib/delayed/worker.rb
index ecc4845a9..bc90b70c4 100644
--- a/lib/delayed/worker.rb
+++ b/lib/delayed/worker.rb
@@ -38,7 +38,7 @@ def self.backend=(backend)
     end
     
     def self.guess_backend
-      self.backend = :active_record if defined?(ActiveRecord)
+      self.backend ||= :active_record if defined?(ActiveRecord)
     end
 
     def initialize(options={})
diff --git a/spec/worker_spec.rb b/spec/worker_spec.rb
index 397e9073f..62bc70edf 100644
--- a/spec/worker_spec.rb
+++ b/spec/worker_spec.rb
@@ -10,10 +10,28 @@
     it "should set the Delayed::Job constant to the backend" do
       Delayed::Job.should == @clazz
     end
-    
+
     it "should set backend with a symbol" do
       Delayed::Worker.backend = :active_record
       Delayed::Worker.backend.should == Delayed::Backend::ActiveRecord::Job
     end
   end
+
+  describe "guess_backend" do
+    after do
+      Delayed::Worker.backend = :active_record
+    end
+
+    it "should set to active_record if nil" do
+      Delayed::Worker.backend = nil
+      lambda {
+        Delayed::Worker.guess_backend
+      }.should change { Delayed::Worker.backend }.to(Delayed::Backend::ActiveRecord::Job)
+    end
+
+    it "should not override the existing backend" do
+      Delayed::Worker.backend = Class.new
+      lambda { Delayed::Worker.guess_backend }.should_not change { Delayed::Worker.backend }
+    end
+  end
 end