Mirror Net::HTTP handling of headers as symbols

  as brought up in #486

lib/webmock/http_lib_adapters/net_http.rb

@@ -273,8 +273,20 @@ def self.request_signature_from_request(net_http, request, body = nil)
 
       headers = Hash[*request.to_hash.map {|k,v| [k, v]}.inject([]) {|r,x| r + x}]
 
-      headers.reject! {|k,v| k =~ /[Aa]uthorization/ && v.first =~ /^Basic / } #we added it to url userinfo
+      # If you try and make a request with headers that are symbols,
+      # Net Http raises the following NoMethodError.
+      #
+      # WebMock normalizes headers when creating a RequestSignature,
+      # and will update all headers from symbols to strings.
+      # This means that you could have a test passing with WebMock, but failing in reality.
+      header_as_symbol = headers.keys.find {|header| header.is_a? Symbol}
+      if header_as_symbol
+        raise NoMethodError.new(
+          "undefined method `split' for :#{header_as_symbol}:Symbol (NoMethodError)`"
+        )
+      end
 
+      headers.reject! {|k,v| k =~ /[Aa]uthorization/ && v.first =~ /^Basic / } #we added it to url userinfo
 
       if request.body_stream
         body = request.body_stream.read

spec/acceptance/net_http/net_http_spec.rb

@@ -9,7 +9,7 @@
 describe "Net:HTTP" do
   include_examples "with WebMock"
 
-  let(:port){ WebMockServer.instance.port }
+  let(:port) { WebMockServer.instance.port }
 
   describe "marshalling" do
     class TestMarshalingInWebMockNetHTTP
@@ -106,6 +106,31 @@ class TestMarshalingInWebMockNetHTTP
     expect(Net::HTTP.start("www.example.com") { |query| query.get("/") }.body).to eq("abc"*100000)
   end
 
+  it "preserves the same functionality as the Net Http library around headers as symbols" do
+    uri = URI.parse("http://google.com/")
+    http = Net::HTTP.new(uri.host, uri.port)
+    request = Net::HTTP::Get.new(uri.request_uri)
+    request[:InvalidHeaderSinceItsASymbol] = "this will not be valid"
+
+    begin
+      http.request(request)
+    rescue => e
+      error_with_webmock = e
+    end
+
+    WebMock.disable!
+
+    begin
+      http.request(request)
+    rescue => e
+      error_without_webmock = e
+    end
+
+    WebMock.enable!
+
+    expect(error_with_webmock.class).to be error_without_webmock.class
+  end
+
   it "should handle multiple values for the same response header" do
     stub_http_request(:get, "www.example.com").to_return(:headers => { 'Set-Cookie' => ['foo=bar', 'bar=bazz'] })
     response = Net::HTTP.get_response(URI.parse("http://www.example.com/"))
@@ -169,6 +194,7 @@ class TestMarshalingInWebMockNetHTTP
       @http.use_ssl = true
       @http.verify_mode = OpenSSL::SSL::VERIFY_NONE
     end
+
     describe "when net http is allowed" do
       it "should not connect to the server until the request", :net_connect => true do
         WebMock.allow_net_connect!