add test for specific background color option

Author: Mifrill

lib/ferrum/page/screenshot.rb

@@ -134,7 +134,7 @@ def validate_background_rgba_color(option)
         option && !(
           option.is_a?(Array) &&
             option.size == 4 &&
-            option.all? { |value| value.is_a?(Integer) }
+            option.all? { |value| value.is_a?(Numeric) }
         )
       end
 

spec/screenshot_spec.rb

@@ -200,6 +200,18 @@ def create_screenshot(**options)
           include_examples 'background_rgba_color ArgumentError' do
             let(:background_rgba_color)  { %w[0 0 0 0] }
           end
+
+          it 'supports screenshotting page with the specific background color' do
+            file = PROJECT_ROOT + "/spec/tmp/screenshot.jpeg"
+            browser.go_to
+            browser.screenshot(path: file)
+            content = File.read(file)
+            browser.screenshot(path: file, background_rgba_color: [0, 0, 0, 0.0])
+            content_with_specific_bc = File.read(file)
+            expect(content).not_to eq(content_with_specific_bc)
+          ensure
+            FileUtils.rm_f([file])
+          end
         end
 
         shared_examples "when scale is set" do