In Ruby 1.9, the "body" of a Rack response cannot be a String.

lib/sham_rack/stub_web_service.rb

@@ -32,7 +32,7 @@ def register_resource(path, content, content_type = "application/xml", status =
         unless request.query_string.to_s.empty?
           request_path += "?" + request.query_string
         end
-        [status, {"Content-Type" => content_type}, content] if request_path == path
+        [status, {"Content-Type" => content_type}, [content]] if request_path == path
       end
     end
 
@@ -43,7 +43,7 @@ def reset
     protected
 
     def default_response
-      [404, {"Content-Type" => "text/plain"}, "Not found"]
+      [404, {"Content-Type" => "text/plain"}, ["Not found"]]
     end
 
   end

spec/sham_rack/stub_web_service_spec.rb

@@ -43,11 +43,11 @@
     before(:each) do
 
       @app.handle do |request|
-        [200, {}, "response from first handler"] if request.get?
+        [200, {}, ["response from first handler"]] if request.get?
       end
 
       @app.handle do |request|
-        [200, {}, "response from second handler"] if request.path_info == "/stuff"
+        [200, {}, ["response from second handler"]] if request.path_info == "/stuff"
       end
 
     end

spec/sham_rack_spec.rb

@@ -107,7 +107,7 @@ def call(env)
         [
           "201 Created", 
           { "Content-Type" => "text/plain", "X-Foo" => "bar" },
-          "BODY"
+          ["BODY"]
         ]
       end
       @response = Net::HTTP.get_response(URI.parse("http://www.test.xyz/"))
@@ -138,7 +138,7 @@ def call(env)
       it "mounts associated block as an app" do
 
         ShamRack.at("simple.xyz") do |env|
-          ["200 OK", { "Content-type" => "text/plain" }, "Easy, huh?"]
+          ["200 OK", { "Content-type" => "text/plain" }, ["Easy, huh?"]]
         end
 
         open("http://simple.xyz").read.should == "Easy, huh?"