Qu doesn't support scheduling, so an exception is raised instead.

lib/qe.rb

@@ -77,4 +77,8 @@ module Qe
   class << self
     attr_accessor :adapter
   end
+
+  # Error that is raised when trying to use a feature
+  # that isn't supported by some adapter.
+  UnsupportedFeatureError = Class.new(StandardError)
 end

lib/qe/qu.rb

@@ -4,8 +4,6 @@
 module Qe
   class Qu
     class Worker
-      include ::Sidekiq::Worker
-
       def self.perform(*args)
         Qe::Worker.perform(*args)
       end
@@ -15,6 +13,10 @@ def self.enqueue(worker, options = {})
       Worker.instance_variable_set("@queue", worker.queue)
       ::Qu.enqueue Worker, worker.name, options
     end
+
+    def self.schedule(*)
+      raise UnsupportedFeatureError, "scheduling isn't supported on Qu"
+    end
   end
 
   self.adapter = Qu

spec/qe/qu_spec.rb

@@ -39,4 +39,12 @@
       Qe::Qu.enqueue(worker, :a => 1)
     end
   end
+
+  context "scheduling" do
+    it "raises exception" do
+      expect {
+        Qe::Qu.schedule(stub, Time.now, :a => 1)
+      }.to raise_error(Qe::UnsupportedFeatureError)
+    end
+  end
 end