dynamically detect which model adapter to use given a class

spec/cancan/ability_spec.rb

@@ -343,6 +343,14 @@ describe CanCan::Ability do
     end
   end
 
+  it "should determine model adapter class by asking AbstractAdapter" do
+    model_class = Object.new
+    adapter_class = Object.new
+    stub(CanCan::ModelAdapters::AbstractAdapter).adapter_class(model_class) { adapter_class }
+    stub(adapter_class).new(model_class, []) { :adapter_instance }
+    @ability.model_adapter(model_class, :read).should == :adapter_instance
+  end
+
   describe "unauthorized message" do
     after(:each) do
       I18n.backend = nil

spec/cancan/model_adapters/active_record_adapter_spec.rb

@@ -33,6 +33,12 @@ if ENV["MODEL_ADAPTER"].nil? || ENV["MODEL_ADAPTER"] == "active_record"
       @comment_table = Comment.table_name
     end
 
+    it "should be for only active record classes" do
+      CanCan::ModelAdapters::ActiveRecordAdapter.should_not be_for_class(Object)
+      CanCan::ModelAdapters::ActiveRecordAdapter.should be_for_class(Article)
+      CanCan::ModelAdapters::AbstractAdapter.adapter_class(Article).should == CanCan::ModelAdapters::ActiveRecordAdapter
+    end
+
     it "should not fetch any records when no abilities are defined" do
       Article.create!
       Article.accessible_by(@ability).should be_empty

spec/cancan/model_adapters/default_adapter_spec.rb

@@ -0,0 +1,7 @@
+require "spec_helper"
+
+describe CanCan::ModelAdapters::DefaultAdapter do
+  it "should be default for generic classes" do
+    CanCan::ModelAdapters::AbstractAdapter.adapter_class(Object).should == CanCan::ModelAdapters::DefaultAdapter
+  end
+end