Add HTTP::Response#content_length

lib/http/response.rb

@@ -86,6 +86,13 @@ def flush
       self
     end
 
+    # Value of the Content-Length header
+    #
+    # @return [Integer]
+    def content_length
+      Integer(headers[Headers::CONTENT_LENGTH]) if headers[Headers::CONTENT_LENGTH]
+    end
+
     # Parsed Content-Type header
     #
     # @return [HTTP::ContentType]

spec/lib/http/response_spec.rb

@@ -28,6 +28,27 @@
     end
   end
 
+  describe "#content_length" do
+    subject { response.content_length }
+
+    context "without Content-Length header" do
+      it { is_expected.to be_nil }
+    end
+
+    context "with Content-Length: 5" do
+      let(:headers) { {"Content-Length" => "5"} }
+      it { is_expected.to eq 5 }
+    end
+
+    context "with Content-Length not an integer" do
+      let(:headers) { {"Content-Length" => "foo"} }
+
+      it "raises an error" do
+        expect { subject }.to raise_error(ArgumentError)
+      end
+    end
+  end
+
   describe "mime_type" do
     subject { response.mime_type }