Implement Capybara::Cuprite::Node#rect (#311)

Closes #276

The implementation's call to [toJSON][] is necessary since the object
returned by [Element.getBoundingClientRect][] is an instance of
[DOMRect][], and is therefore unable to have its keys iterated and
serialized back to Cuprite on its own.

[Element.getBoundingClientRect]: https://developer.mozilla.org/en-US/docs/Web/API/Element/getBoundingClientRect
[DOMRect]: https://developer.mozilla.org/en-US/docs/Web/API/DOMRect
[toJSON]: segment-boneyard/nightmare#723 (comment)

Author: seanpdoyle

CHANGELOG.md

@@ -3,6 +3,7 @@
 ### Added
 - Support time inputs [#245]
 - Add initial support for shadow_root [#234]
+- Support `Capybara::Cuprite::Node#rect` [#276]
 
 ### Changed
 

lib/capybara/cuprite/node.rb

@@ -236,6 +236,12 @@ def shadow_root
         root && self.class.new(driver, root.node)
       end
 
+      def rect
+        driver.evaluate_script <<~JS, self
+          arguments[0].getBoundingClientRect().toJSON()
+        JS
+      end
+
       def inspect
         %(#<#{self.class} @node=#{@node.inspect}>)
       end

spec/features/driver_spec.rb

@@ -1447,6 +1447,20 @@ def create_screenshot(file, *args)
         end
       end
 
+      context "find" do
+        before { @session.visit("/cuprite/click_coordinates") }
+
+        it "supports position filters" do
+          box = @session.find(:css, "#box")
+          log = @session.find(:css, "#log")
+
+          expect(@session).to have_element(id: "box", above: log)
+          expect(@session).to have_element(id: "log", below: box)
+          expect(@session).not_to have_element(id: "box", below: log)
+          expect(@session).not_to have_element(id: "log", above: box)
+        end
+      end
+
       context "set" do
         before { @session.visit("/cuprite/set") }