added specs, fix #3

lib/guard/rails-assets.rb

@@ -34,8 +34,6 @@ module Guard
       end
     end
 
-    private
-
     def run_for? command
       run_on = @options[:run_on]
       run_on = [:start, :change] if not run_on or run_on.to_s.empty?

spec/guard/rails-assets_spec.rb

@@ -21,6 +21,19 @@ describe Guard::RailsAssets do
     it_behaves_like 'guard command', :command => :run_on_change, :run => true
   end
 
+  describe 'run options' do
+    it 'should allow array of symbols' do
+      guard = Guard::RailsAssets.new(['watchers'], :run_on => [:start, :change])
+      guard.run_for?(:start).should be_true
+      guard.run_for?(:reload).should be_false
+    end
+
+    it 'should allow symbol' do
+      guard = Guard::RailsAssets.new(['watchers'], :run_on => :start)
+      guard.run_for?(:start).should be_true
+      guard.run_for?(:reload).should be_false
+    end
+  end
 
   describe 'asset compilation using CLI' do
     def stub_system_with result