The default stubbed response body, which is an empty String, is utf-8…

… encoded.

lib/webmock/response.rb

@@ -38,7 +38,7 @@ def headers=(headers)
     end
 
     def body
-      @body || String.new
+      @body || String.new("")
     end
 
     def body=(body)

spec/unit/response_spec.rb

@@ -105,6 +105,10 @@
       expect(@response.body).to_not be_frozen
     end
 
+    it "shoud return utf-8 encoded string by default" do
+      expect(@response.body.encoding).to eq(Encoding::UTF_8)
+    end
+
     it "should report body if assigned" do
       @response = WebMock::Response.new(body: "abc")
       expect(@response.body).to eq("abc")