Error on invalid body

lib/webmock/response.rb

@@ -43,6 +43,7 @@ def body
 
     def body=(body)
       @body = body
+      assert_valid_body!
       stringify_body!
     end
 
@@ -109,6 +110,13 @@ def stringify_body!
       end
     end
 
+    def assert_valid_body!
+      valid_types = [Proc, IO, Pathname, String, Array]
+      return if @body.nil?
+      return if valid_types.any? { |c| @body.is_a?(c) }
+      raise InvalidBody, "must be one of: #{valid_types}. '#{@body.class}' given"
+    end
+
     def read_raw_response(raw_response)
       if raw_response.is_a?(IO)
         string = raw_response.read
@@ -129,6 +137,8 @@ def read_raw_response(raw_response)
       options
     end
 
+    InvalidBody = Class.new(StandardError)
+
   end
 
   class DynamicResponse < Response

spec/unit/request_pattern_spec.rb

@@ -400,7 +400,7 @@ def match(request_signature)
                                                              :headers => {:content_type => 'application/json'}, :body => "foo bar"))
           end
 
-          it "shound not match if request body is different" do
+          it "should not match if request body is different" do
             WebMock::RequestPattern.new(:post, 'www.example.com', :body => {:a => 1, :b => 2}).
               should_not match(WebMock::RequestSignature.new(:post, "www.example.com",
               :headers => {:content_type => 'application/json'}, :body => "{\"a\":1,\"c\":null}"))

spec/unit/response_spec.rb

@@ -124,6 +124,15 @@
       @response = WebMock::Response.new(:body => Pathname.new(__FILE__))
       @response.body.should == File.read(__FILE__)
     end
+
+    # Users of webmock commonly make the mistake of stubbing the response
+    # body to return a hash, to prevent this:
+    #
+    it "should error if not given one of the allowed types" do
+      lambda { WebMock::Response.new(:body => Hash.new) }.should \
+        raise_error(WebMock::Response::InvalidBody)
+    end
+
   end
 
   describe "from raw response" do