Support have_http_status with Rack::MockResponse

lib/rspec/rails/matchers/have_http_status.rb

@@ -49,6 +49,12 @@ def as_test_response(obj)
               resp.request = ActionDispatch::Request.new({})
             end
             ::ActionDispatch::TestResponse.from_response(obj)
+          elsif obj.respond_to?(:status) && obj.respond_to?(:headers) && obj.respond_to?(:body)
+            # Hack to support `Rack::MockResponse` without having to load
+            # Rack or catch `NameError`s for the undefined constants
+            resp = ::ActionDispatch::Response.new(obj.status, obj.headers, obj.body)
+            resp.request = ::ActionDispatch::Request.new({})
+            ::ActionDispatch::TestResponse.from_response(obj)
           else
             raise TypeError, "Invalid response type: #{obj}"
           end

spec/rspec/rails/matchers/have_http_status_spec.rb

@@ -39,6 +39,19 @@ def create_response(opts = {})
       end
     end
 
+    context "given something that acts as a Rack::MockResponse" do
+      it "returns true for a response with the same code" do
+        response = instance_double(
+          '::Rack::MockResponse',
+          status: code,
+          headers: {},
+          body: ""
+        )
+
+        expect(matcher.matches?(response)).to be(true)
+      end
+    end
+
     it "returns false given another type" do
       response = Object.new