Add ISpecFlowOutputHelper test

SpecFlow.DependencyInjection.Tests/ISpecFlowOutputHelper.feature

@@ -0,0 +1,8 @@
+Feature: ISpecFlowOutputHelper
+    Issue #75: ITestOutputHelper unavailable when using SpecFlow.xUnit
+    https://github.com/solidtoken/SpecFlow.DependencyInjection/issues/75
+
+Scenario: Assert ISpecFlowOutputHelper Is Available
+    The When part here is purely for displaying the message using ISpecFlowOutputHelper
+    When a message is output using ISpecFlowOutputHelper
+    Then verify that ISpecFlowOutputHelper is correctly injected

SpecFlow.DependencyInjection.Tests/ISpecFlowOutputHelperSteps.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using TechTalk.SpecFlow;
+using TechTalk.SpecFlow.Infrastructure;
+using Xunit;
+
+namespace SolidToken.SpecFlow.DependencyInjection.Tests
+{
+    [Binding]
+    public class ISpecFlowOutputHelperSteps
+    {
+        private readonly ISpecFlowOutputHelper _output;
+
+        public ISpecFlowOutputHelperSteps(ISpecFlowOutputHelper output)
+        {
+            _output = output;
+        }
+
+        [When(@"a message is output using ISpecFlowOutputHelper")]
+        public void WhenAMessageIsOutputUsingISpecFlowOutputHelper()
+        {
+            _output.WriteLine("This is output from ISpecFlowOutputHelper");
+        }
+
+        [Then(@"verify that ISpecFlowOutputHelper is correctly injected")]
+        public void ThenVerifyThatISpecFlowOutputHelperIsCorrectlyInjected()
+        {
+            Assert.NotNull(_output);
+        }
+    }
+}

SpecFlow.DependencyInjection.Tests/TestDependencies.cs

@@ -1,6 +1,4 @@
-using System;
-using System.Linq;
-using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection;
 
 namespace SolidToken.SpecFlow.DependencyInjection.Tests
 {