Validate if proc arity (argument count) - must be 1

lib/clockwork/event.rb

@@ -74,8 +74,9 @@ def run_if?(t)
     end
 
     def validate_if_option(if_option)
-      if if_option && !if_option.respond_to?(:call)
-        raise ArgumentError.new(':if expects a callable object, but #{if_option} does not respond to call')
+      return unless if_option
+      unless if_option.respond_to?(:call) && if_option.respond_to?(:arity) && if_option.arity == 1
+        raise ArgumentError.new(':if expects a callable object that accepts a single argument, but #{if_option} is not')
       end
     end
   end

test/manager_test.rb

@@ -260,6 +260,22 @@ def assert_wont_run(t)
         @manager.every(1.second, 'myjob', :if => true)
       end
     end
+
+    it ":if does not respond to arity then raise ArgumentError" do
+      assert_raises(ArgumentError) do
+        callable = Class.new do
+          def call; end
+        end
+
+        @manager.every(1.second, 'myjob', :if => callable.new)
+      end
+    end
+
+    it ":if does not have an arity of 1 then raise ArgumentError" do
+      assert_raises(ArgumentError) do
+        @manager.every(1.second, 'myjob', :if => lambda {})
+      end
+    end
   end
 
   describe "max_threads" do