Only try to inverse translate if the dictionary is set up

src/RdbmsEventStore.Tests/RdbmsEventStore.Tests.csproj

@@ -8,6 +8,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.3.0" />
+    <PackageReference Include="Moq" Version="4.7.137" />
     <PackageReference Include="xunit" Version="2.2.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.2.0" />
   </ItemGroup>

src/RdbmsEventStore.Tests/TranslatingEventRegistryTests.cs

@@ -0,0 +1,82 @@
+using System.Collections.Generic;
+using Moq;
+using RdbmsEventStore.EventRegistry;
+using Xunit;
+
+namespace RdbmsEventStore.Tests
+{
+    public class TranslatingEventRegistryTests
+    {
+        private class Foo { }
+
+        public class UnidirectionalTranslations
+        {
+            private readonly TranslatingEventRegistry _registry;
+
+            public UnidirectionalTranslations()
+            {
+                var innerRegistry = new Mock<IComposableEventRegistry>(MockBehavior.Strict);
+                innerRegistry.Setup(r => r.NameFor(typeof(Foo))).Returns(nameof(Foo));
+                innerRegistry.Setup(r => r.TypeFor(nameof(Foo))).Returns(typeof(Foo));
+
+                _registry = new TranslatingEventRegistry(new Dictionary<string, string>
+                {
+                    {"Bar", "Foo"}
+                }, innerRegistry.Object);
+            }
+
+            [Fact]
+            public void CanReturnTypesNotRegisteredInTranslations()
+            {
+                Assert.Equal(typeof(Foo), _registry.TypeFor(nameof(Foo)));
+            }
+
+            [Fact]
+            public void CanReturnTypesRegisteredInTranslations()
+            {
+                Assert.Equal(typeof(Foo), _registry.TypeFor("Bar"));
+            }
+
+            [Fact]
+            public void ReturnsNewName()
+            {
+                Assert.Equal(nameof(Foo), _registry.NameFor(typeof(Foo)));
+            }
+        }
+
+        public class BidirectionalTranslations
+        {
+            private readonly TranslatingEventRegistry _registry;
+
+            public BidirectionalTranslations()
+            {
+                var innerRegistry = new Mock<IComposableEventRegistry>(MockBehavior.Strict);
+                innerRegistry.Setup(r => r.NameFor(typeof(Foo))).Returns(nameof(Foo));
+                innerRegistry.Setup(r => r.TypeFor(nameof(Foo))).Returns(typeof(Foo));
+
+                _registry = new TranslatingEventRegistry(new Dictionary<string, string>
+                {
+                    {"Bar", "Foo"}
+                }, innerRegistry.Object, translateNewEvents: true);
+            }
+
+            [Fact]
+            public void CanReturnTypesNotRegisteredInTranslations()
+            {
+                Assert.Equal(typeof(Foo), _registry.TypeFor(nameof(Foo)));
+            }
+
+            [Fact]
+            public void CanReturnTypesRegisteredInTranslations()
+            {
+                Assert.Equal(typeof(Foo), _registry.TypeFor("Bar"));
+            }
+
+            [Fact]
+            public void ReturnsOldName()
+            {
+                Assert.Equal("Bar", _registry.NameFor(typeof(Foo)));
+            }
+        }
+    }
+}

src/RdbmsEventStore/EventRegistry/TranslatingEventRegistry.cs

@@ -44,7 +44,7 @@ private string TranslationFor(string eventType)
                 : eventType;
 
         private string InverseTranslationFor(string eventType)
-            => _inverseTranslations.TryGetValue(eventType, out var translated)
+            => _translateNewEvents && _inverseTranslations.TryGetValue(eventType, out var translated)
                 ? InverseTranslationFor(translated)
                 : eventType;