switched assert example to check cowfile

lib/cowsay.rb

@@ -8,12 +8,14 @@ def initialize(options={})
     end
 
     def say(message, options={})
-      out = options[:out]
-      assert(out.nil? || out.respond_to?(:<<))
+      assert(options[:cowfile].nil? || File.exist?(options[:cowfile]))
       command = "cowsay"
       if options[:strings] && options[:strings][:eyes]
         command << " -e '#{options[:strings][:eyes]}'"
       end
+      if options[:cowfile]
+        command << " -f #{options[:cowfile]}"
+      end
 
       messages = case message
                  when Array then message
@@ -33,8 +35,8 @@ def say(message, options={})
         end
       end
       output = results.join("\n")    
-      if out
-        out << output
+      if options[:out]
+        options[:out] << output
       end
       destination = case options[:out]
                     when nil  then "return value"

spec/cowsay_spec.rb

@@ -110,11 +110,20 @@ def set_child_exit_status(status)
       end
     end
 
-    context "bad :out option" do
-      it "should raise ArgumentError" do
+    context "given a cowfile" do
+      it "should supply a -f argument on the command line" do
+        File.stub!(:exist?).and_return(true)
+        @io_class.should_receive(:popen).with(/-f COWFILE/, anything)
+        @it.say("moo", :cowfile => "COWFILE")
+      end
+    end
+
+    context "given an invalid cowfile" do
+      it "should raise an error" do
+        File.stub!(:exist?).and_return(false)
         lambda do
-          @it.say("whatever", :out => Object.new)
-        end.should raise_error
+          @it.say("moo", :cowfile => "COWFILE")
+        end.should raise_error(Exception)
       end
     end
   end