Raise an exception when trying to use an :at with the cron shortcuts.

lib/outputs/cron.rb

@@ -27,7 +27,7 @@ module Whenever
     protected
 
       def parse_symbol
-        case @time
+        shortcut = case @time
           when :reboot          then '@reboot'
           when :year, :yearly   then '@annually'
           when :day, :daily     then '@daily'
@@ -35,7 +35,16 @@ module Whenever
           when :month, :monthly then '@monthly'
           when :week, :weekly   then '@weekly'
           when :hour, :hourly   then '@hourly'
-          else parse_as_string
+        end
+        
+        if shortcut
+          if @at > 0
+            raise ArgumentError, "You cannot specify an ':at' when using the shortcuts for times."
+          else
+            return shortcut
+          end
+        else
+          parse_as_string
         end
       end
 

test/cron_test.rb

@@ -167,6 +167,35 @@ class CronTest < Test::Unit::TestCase
     end
   end
   
+  context "When parsing time using the cron shortcuts" do
+    should "parse a :symbol into the correct shortcut" do
+      assert_equal '@reboot',   parse_time(:reboot)
+      assert_equal '@annually', parse_time(:year)
+      assert_equal '@annually', parse_time(:yearly)
+      assert_equal '@daily',    parse_time(:day)
+      assert_equal '@daily',    parse_time(:daily)
+      assert_equal '@midnight', parse_time(:midnight)
+      assert_equal '@monthly',  parse_time(:month)
+      assert_equal '@monthly',  parse_time(:monthly)
+      assert_equal '@hourly',   parse_time(:hour)
+      assert_equal '@hourly',   parse_time(:hourly)
+    end
+    
+    should "raise an exception if a valid shortcut is given but also an :at" do
+      assert_raises ArgumentError do
+        parse_time(:hour, nil, "1:00 am")
+      end
+      
+      assert_raises ArgumentError do
+        parse_time(:reboot, nil, 5)
+      end
+      
+      assert_raises ArgumentError do
+        parse_time(:day, nil, '4:20pm')
+      end
+    end
+  end
+
 private
 
   def assert_days_and_hours_and_minutes_equals(expected, time)