Merge pull request #224 from graemefoster/bug-concurrency-issue-on-context-lookup

Test / fix for concurrency issue when using bddfy with parallel runners

Author: mwhelan

src/TestStack.BDDfy.Tests/Concurrency/ParallelRunnerScenario.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Linq;
+using System.Threading.Tasks;
+using TestStack.BDDfy.Tests.Stories;
+using Xunit;
+
+namespace TestStack.BDDfy.Tests.Concurrency
+{
+    public class ParallelRunnerScenario
+    {
+        [Fact]
+        public async Task CanHandleMultipleThreadsExecutingBddfyConcurrently()
+        {
+            try
+            {
+                await Task.WhenAll(
+                    Enumerable.Range(0, 100)
+                        .Select(_ => Task.Run(() => new DummyScenario().BDDfy<ParallelRunnerScenario>())));
+            }
+            catch (Exception e)
+            {
+                Assert.False(true, "Threw exception " + e);
+            }
+        }
+    }
+}

src/TestStack.BDDfy.Tests/TestStack.BDDfy.Tests.csproj

@@ -70,6 +70,7 @@
     <Compile Include="Arguments\ArgumentsProvidedForGiven.cs" />
     <Compile Include="Arguments\ArgumentsProvidedForThen.cs" />
     <Compile Include="Arguments\MultipleArgumentsProvidedForTheSameStep.cs" />
+    <Compile Include="Concurrency\ParallelRunnerScenario.cs" />
     <Compile Include="Configuration\EmptyScenario.cs" />
     <Compile Include="Configuration\SequentialKeyGeneratorTests.cs" />
     <Compile Include="Configuration\StepExecutorTests.cs" />
@@ -192,6 +193,7 @@
     <Content Include="TagsTests.TagsAreReportedInHtmlReport.approved.txt" />
     <Content Include="TagsTests.TagsAreReportedInTextReport.approved.txt" />
   </ItemGroup>
+  <ItemGroup />
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">
     <PropertyGroup>

src/TestStack.BDDfy/TestContext.cs

@@ -5,6 +5,7 @@ namespace TestStack.BDDfy
     public class TestContext : ITestContext
     {
         private static readonly Dictionary<object, ITestContext> ContextLookup = new Dictionary<object, ITestContext>();
+        private static object _dictionaryLock = new object();
 
         private TestContext(object testObject)
         {
@@ -17,15 +18,18 @@ public static void SetContext(object testObject, ITestContext context)
             var fluentBuilder = testObject as IFluentStepBuilder;
             if (fluentBuilder != null) testObject = fluentBuilder.TestObject;
 
-            if (ContextLookup.ContainsKey(testObject))
+            lock (_dictionaryLock)
             {
-                var oldContext = ContextLookup[testObject];
-                context.Examples = oldContext.Examples;
-                ContextLookup[testObject] = new TestContext(testObject);
-            }
-            else
-            {
-                ContextLookup.Add(testObject, context);
+                if (ContextLookup.ContainsKey(testObject))
+                {
+                    var oldContext = ContextLookup[testObject];
+                    context.Examples = oldContext.Examples;
+                    ContextLookup[testObject] = new TestContext(testObject);
+                }
+                else
+                {
+                    ContextLookup.Add(testObject, context);
+                }
             }
         }
 
@@ -34,16 +38,22 @@ public static ITestContext GetContext(object testObject)
             var fluentBuilder = testObject as IFluentStepBuilder;
             if (fluentBuilder != null) testObject = fluentBuilder.TestObject;
 
-            if (!ContextLookup.ContainsKey(testObject))
-                ContextLookup.Add(testObject, new TestContext(testObject));
+            lock (_dictionaryLock)
+            {
+                if (!ContextLookup.ContainsKey(testObject))
+                    ContextLookup.Add(testObject, new TestContext(testObject));
 
-            return ContextLookup[testObject];
+                return ContextLookup[testObject];
+            }
         }
 
         public static void ClearContextFor(object testObject)
         {
-            if (ContextLookup.ContainsKey(testObject))
-                ContextLookup.Remove(testObject);
+            lock (_dictionaryLock)
+            {
+                if (ContextLookup.ContainsKey(testObject))
+                    ContextLookup.Remove(testObject);
+            }
         }
 
         public ExampleTable Examples { get; set; }