Add #exception to the test case yielded to blocks

Fixes #823

lib/cucumber/running_test_case.rb

@@ -19,7 +19,7 @@ module Cucumber
   # you get a couple of extra methods.
   module RunningTestCase
     def self.new(test_case)
-      Builder.new(test_case).result
+      Builder.new(test_case).running_test_case
     end
 
     class Builder
@@ -45,7 +45,7 @@ def examples_table(examples_table)
       def examples_table_row(row)
       end
 
-      def result
+      def running_test_case
         @factory.new(@test_case)
       end
     end
@@ -62,6 +62,11 @@ def accept_hook?(hook)
         hook.tag_expressions.all? { |expression| @test_case.match_tags?(expression) }
       end
 
+      def exception
+        return unless @result.failed?
+        @result.exception
+      end
+
       def failed?
         @result.failed?
       end

spec/cucumber/running_test_case_spec.rb

@@ -44,6 +44,56 @@ module Cucumber
       end
     end
 
+    context "for a failed scenario" do
+      let(:gherkin_doc) do
+        gherkin do
+          feature "feature name" do
+            scenario "scenario name" do
+              step "failed"
+            end
+          end
+        end
+      end
+
+      let(:exception) { StandardError.new }
+
+      before do
+        self.wrapped_test_case = self.wrapped_test_case.with_result(Core::Test::Result::Failed.new(0, exception))
+      end
+
+      it "is failed?" do
+        expect(wrapped_test_case.failed?).to be_truthy
+      end
+
+      it "exposes the exception" do
+        expect(wrapped_test_case.exception).to eq exception
+      end
+    end
+
+    context "for a passing scenario" do
+      let(:gherkin_doc) do
+        gherkin do
+          feature "feature name" do
+            scenario "scenario name" do
+              step "passing"
+            end
+          end
+        end
+      end
+
+      before do
+        self.wrapped_test_case = self.wrapped_test_case.with_result(Core::Test::Result::Passed.new(0))
+      end
+
+      it "is not failed?" do
+        expect(wrapped_test_case.failed?).to be_falsey
+      end
+
+      it "#exception is nil" do
+        expect(wrapped_test_case.exception).to be_nil
+      end
+    end
+
     context "for a scenario outline" do
       let(:gherkin_doc) do
         gherkin do