Make SuperDiff respect extra_failure_lines metadata of RSpec

Fix splitwise#108

lib/super_diff/rspec/monkey_patches.rb

@@ -218,7 +218,10 @@ def failure_line_groups
                   }
                 end
               end
-
+              @failure_line_groups << {
+                lines: extra_failure_lines,
+                already_colorized: true
+              }
               @failure_line_groups
             end
           end

spec/integration/rspec/metadata_spec.rb

@@ -0,0 +1,21 @@
+require "spec_helper"
+
+RSpec.describe "Integration with RSpec metadata for extra failure lines",
+               type: :integration do
+  it "displays extra_failure_lines of metadata" do
+    as_both_colored_and_uncolored do |color_enabled|
+      program =
+        make_plain_test_program(<<~TEST, color_enabled: color_enabled, preserve_as_whole_file: true)
+          RSpec.describe "test" do
+            it { expect(true).to be(false) }
+
+            after do
+              RSpec.current_example.metadata[:extra_failure_lines] = "foo\nbar"  
+            end
+          end
+        TEST
+
+      expect(program).to produce_output_when_run("foo\nbar").in_color(color_enabled)
+    end
+  end
+end