diff --git a/lib/httparty.rb b/lib/httparty.rb
index 3f79147..d5aee4d 100644
--- a/lib/httparty.rb
+++ b/lib/httparty.rb
@@ -16,12 +16,16 @@ module HTTParty
     base.extend ClassMethods
   end
   
-  module ClassMethods
+  class UnsupportedFormat < StandardError; end
+  
+  AllowedFormats = %w[xml json]
+  
+  module ClassMethods    
     def base_uri(base_uri=nil)
       return @base_uri unless base_uri
       # don't want this to ever end with /
       base_uri = base_uri.ends_with?('/') ? base_uri.chop : base_uri
-      @base_uri = ensure_http(base_uri)
+      @base_uri = normalize_base_uri(base_uri)
     end
     
     def basic_auth(u, p)
@@ -39,13 +43,11 @@ module HTTParty
       @http
     end
     
-    def headers
-      @headers ||= {}
-    end
-    
-    def headers=(h)
+    def headers(h={})
       raise ArgumentError, 'Headers must be a hash' unless h.is_a?(Hash)
-      headers.merge!(h)
+      @headers ||= {}
+      return @headers if h.blank?
+      @headers.merge!(h)
     end
     
     def get(path, options={})
@@ -64,8 +66,10 @@ module HTTParty
       send_request 'delete', path, options
     end
     
-    def format(f=nil)
-      @format = f.to_s
+    def format(f)
+      f = f.to_s
+      raise UnsupportedFormat, "Must be one of: #{AllowedFormats.join(', ')}" unless AllowedFormats.include?(f)
+      @format = f
     end
     
     private
@@ -84,23 +88,24 @@ module HTTParty
         request.body = options[:body] unless options[:body].blank?
         request.initialize_http_header headers.merge(options[:headers] || {})
         request.basic_auth(@auth[:username], @auth[:password]) if @auth
-        @response    = http.start() { |conn| conn.request(request) }
-        parse(@response.body)
+        response     = http.start() { |conn| conn.request(request) }
+        parse_response(response.body)
       end
       
-      def parse(body)
+      def parse_response(body)
         case @format
         when 'xml'
           Hash.from_xml(body)
         when 'json'
           ActiveSupport::JSON.decode(body)
         else
+          # just return the response if no format 
           body
         end
       end
     
       # Makes it so uri is sure to parse stuff like google.com with the http
-      def ensure_http(str)
+      def normalize_base_uri(str)
         str =~ /^https?:\/\// ? str : "http#{'s' if str.include?(':443')}://#{str}"
       end
       
@@ -109,14 +114,8 @@ module HTTParty
       #   /foobar.xml => 'xml'
       #   /foobar.json => 'json'
       def format_from_path(path)
-        return case path
-        when /\.xml$/
-          'xml'
-        when /\.json$/
-          'json'
-        else
-          nil
-        end
+        ext = File.extname(path)[1..-1]
+        !ext.blank? && AllowedFormats.include?(ext) ? ext : nil
       end
   end
 end
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diff --git a/spec/hash_spec.rb b/spec/hash_spec.rb
new file mode 100644
index 0000000..775b718
--- /dev/null
+++ b/spec/hash_spec.rb
@@ -0,0 +1,11 @@
+require File.join(File.dirname(__FILE__), 'spec_helper')
+
+describe HTTParty::CoreExt::HashConversions do
+  it "should convert hash to struct" do
+    {'foo' => 'bar'}.to_struct.should == OpenStruct.new(:foo => 'bar')
+  end
+  
+  it 'should convert nested hash to struct' do
+    {'foo' => {'bar' => 'baz'}}.to_struct.should == OpenStruct.new(:foo => OpenStruct.new(:bar => 'baz'))
+  end
+end
\ No newline at end of file
diff --git a/spec/httparty_spec.rb b/spec/httparty_spec.rb
index f8b251b..3274434 100644
--- a/spec/httparty_spec.rb
+++ b/spec/httparty_spec.rb
@@ -36,9 +36,75 @@ describe HTTParty do
     end
   end
   
+  it "should initialize headers to empty hash" do
+    Foo.headers.should == {}
+  end
+  
+  it "should allow updating the headers" do
+    init_headers = {:foo => 'bar', :baz => 'spax'}
+    Foo.headers init_headers
+    Foo.headers.should == init_headers
+  end
+  
   it 'should be able to set basic authentication' do
     Foo.basic_auth 'foobar', 'secret'
     Foo.instance_variable_get("@auth").should == {:username => 'foobar', :password => 'secret'}
   end
   
+  describe "format" do
+    it "should allow xml" do
+      Foo.format :xml
+      Foo.instance_variable_get("@format").should == 'xml'
+    end
+    
+    it "should allow json" do
+      Foo.format :json
+      Foo.instance_variable_get("@format").should == 'json'
+    end
+    
+    it 'should not allow funky format' do
+      lambda do
+        Foo.format :foobar
+      end.should raise_error(HTTParty::UnsupportedFormat)
+    end
+  end
+  
+  describe "deriving format from path" do
+    it "should work if there is extension and extension is an allowed format" do
+      %w[xml json].each do |ext|
+        Foo.send(:format_from_path, "/foo/bar.#{ext}").should == ext
+      end
+    end
+    
+    it "should NOT work if there is extension but extention is not allow format" do
+      Foo.send(:format_from_path, '/foo/bar.php').should == nil
+    end
+    
+    it 'should NOT work if there is no extension' do
+      ['', '.'].each do |ext|
+        Foo.send(:format_from_path, "/foo/bar#{ext}").should == nil
+      end
+    end
+  end
+  
+  describe 'parsing responses' do
+    it 'should parse xml automatically' do
+      xml = <<EOF
+<books>
+  <book>
+    <id>1234</id>
+    <name>Foo Bar!</name>
+  </book>
+</books>
+EOF
+      Foo.format :xml
+      Foo.send(:parse_response, xml).should == {'books' => {'book' => {'id' => '1234', 'name' => 'Foo Bar!'}}}
+    end
+    
+    it 'should parse json automatically' do
+      json = %q[{"books": {"book": {"name": "Foo Bar!", "id": "1234"}}}]
+      Foo.format :json
+      Foo.send(:parse_response, json).should == {'books' => {'book' => {'id' => '1234', 'name' => 'Foo Bar!'}}}
+    end
+  end
 end
\ No newline at end of file