diff --git a/Octokit.Tests.Conventions/Exception/InterfaceHasAdditionalMethodsException.cs b/Octokit.Tests.Conventions/Exception/InterfaceHasAdditionalMethodsException.cs
new file mode 100644
index 00000000..4bccc557
--- /dev/null
+++ b/Octokit.Tests.Conventions/Exception/InterfaceHasAdditionalMethodsException.cs
@@ -0,0 +1,25 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.Serialization;
+
+namespace Octokit.Tests.Conventions
+{
+    public class InterfaceHasAdditionalMethodsException : Exception
+    {
+        public InterfaceHasAdditionalMethodsException(Type type, IEnumerable<string> methodsMissingOnReactiveClient)
+            : base(CreateMessage(type, methodsMissingOnReactiveClient)) { }
+
+        public InterfaceHasAdditionalMethodsException(Type type, IEnumerable<string> methodsMissingOnReactiveClient, Exception innerException)
+            : base(CreateMessage(type, methodsMissingOnReactiveClient), innerException) { }
+
+        protected InterfaceHasAdditionalMethodsException(SerializationInfo info, StreamingContext context)
+            : base(info, context) { }
+
+        static string CreateMessage(Type type, IEnumerable<string> methods)
+        {
+            var methodsFormatted = String.Join("\r\n", methods.Select(m => String.Format(" - {0}", m)));
+            return String.Format("Methods found on type {0} which should be removed:\r\n{1}", type.Name, methodsFormatted);
+        }
+    }
+}
\ No newline at end of file
diff --git a/Octokit.Tests.Conventions/Exception/InterfaceMissingMethodsException.cs b/Octokit.Tests.Conventions/Exception/InterfaceMissingMethodsException.cs
new file mode 100644
index 00000000..65fc8c76
--- /dev/null
+++ b/Octokit.Tests.Conventions/Exception/InterfaceMissingMethodsException.cs
@@ -0,0 +1,25 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.Serialization;
+
+namespace Octokit.Tests.Conventions
+{
+    public class InterfaceMissingMethodsException : Exception
+    {
+        public InterfaceMissingMethodsException(Type type, IEnumerable<string> methodsMissingOnReactiveClient)
+            : base(CreateMessage(type, methodsMissingOnReactiveClient)) { }
+
+        public InterfaceMissingMethodsException(Type type, IEnumerable<string> methodsMissingOnReactiveClient, Exception innerException)
+            : base(CreateMessage(type, methodsMissingOnReactiveClient), innerException) { }
+
+        protected InterfaceMissingMethodsException(SerializationInfo info, StreamingContext context)
+            : base(info, context) { }
+
+        static string CreateMessage(Type type, IEnumerable<string> methods)
+        {
+            var methodsFormatted = String.Join("\r\n", methods.Select(m => String.Format(" - {0}", m)));
+            return String.Format("Methods not found on interface {0} which are required:\r\n{1}", type.Name, methodsFormatted);
+        }
+    }
+}
\ No newline at end of file
diff --git a/Octokit.Tests.Conventions/Exception/InterfaceNotFoundException.cs b/Octokit.Tests.Conventions/Exception/InterfaceNotFoundException.cs
new file mode 100644
index 00000000..3a428331
--- /dev/null
+++ b/Octokit.Tests.Conventions/Exception/InterfaceNotFoundException.cs
@@ -0,0 +1,25 @@
+using System;
+using System.Runtime.Serialization;
+
+namespace Octokit.Tests.Conventions
+{
+    public class InterfaceNotFoundException : Exception
+    {
+        public InterfaceNotFoundException() { }
+
+        public InterfaceNotFoundException(string type)
+            : base(CreateMessage(type)) { }
+
+        public InterfaceNotFoundException(string type, Exception innerException)
+            : base(CreateMessage(type), innerException) { }
+
+        protected InterfaceNotFoundException(SerializationInfo info, StreamingContext context)
+            : base(info, context) { }
+
+        static string CreateMessage(string type)
+        {
+            return String.Format("Could not find the interface {0}. Add this to the Octokit.Reactive project", type);
+        }
+
+    }
+}
diff --git a/Octokit.Tests.Conventions/Octokit.Tests.Conventions.csproj b/Octokit.Tests.Conventions/Octokit.Tests.Conventions.csproj
index 7b378297..8979df85 100644
--- a/Octokit.Tests.Conventions/Octokit.Tests.Conventions.csproj
+++ b/Octokit.Tests.Conventions/Octokit.Tests.Conventions.csproj
@@ -50,6 +50,9 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="DebuggerDisplayOnModels.cs" />
+    <Compile Include="Exception\InterfaceHasAdditionalMethodsException.cs" />
+    <Compile Include="Exception\InterfaceMissingMethodsException.cs" />
+    <Compile Include="Exception\InterfaceNotFoundException.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="SyncObservableClients.cs" />
     <Compile Include="TypeExtensions.cs" />
diff --git a/Octokit.Tests.Conventions/SyncObservableClients.cs b/Octokit.Tests.Conventions/SyncObservableClients.cs
index 376750ac..c78e5a47 100644
--- a/Octokit.Tests.Conventions/SyncObservableClients.cs
+++ b/Octokit.Tests.Conventions/SyncObservableClients.cs
@@ -13,23 +13,30 @@ namespace Octokit.Tests.Conventions
 {
     public class SyncObservableClients
     {
-        [Fact]
-        private void CheckObservableClientExample()
-        {
-            CheckObservableClients(typeof(ISearchClient));
-        }
-
         [Theory]
         [ClassData(typeof(ClientInterfaces))]
-        private void CheckObservableClients(Type clientInterface)
+        public void CheckObservableClients(Type clientInterface)
         {
             var observableClient = clientInterface.GetObservableClientInterface();
             var mainMethods = clientInterface.GetMethodsOrdered();
             var observableMethods = observableClient.GetMethodsOrdered();
             var mainNames = Array.ConvertAll(mainMethods, m => m.Name);
             var observableNames = Array.ConvertAll(observableMethods, m => m.Name);
-            AssertEx.Empty(observableNames.Except(mainNames), "Extra observable methods");
-            AssertEx.Empty(mainNames.Except(observableNames), "Missing observable methods");
+
+            var methodsMissingOnReactiveClient = mainNames.Except(observableNames);
+
+            if (methodsMissingOnReactiveClient.Any())
+            {
+                throw new InterfaceMissingMethodsException(observableClient, methodsMissingOnReactiveClient);
+            }
+
+            var additionalMethodsOnReactiveClient = observableNames.Except(mainNames);
+
+            if (additionalMethodsOnReactiveClient.Any())
+            {
+                throw new InterfaceHasAdditionalMethodsException(observableClient, additionalMethodsOnReactiveClient);
+            }
+
             int index = 0;
             foreach(var mainMethod in mainMethods)
             {
@@ -88,7 +95,7 @@ namespace Octokit.Tests.Conventions
             {
                 var observableParameter = observableParameters[index];
                 Assert.Equal(mainParameter.Name, observableParameter.Name);
-                var mainType = mainParameter.ParameterType; 
+                var mainType = mainParameter.ParameterType;
                 var typeInfo = mainType.GetTypeInfo();
                 var expectedType = GetObservableExpectedType(mainType);
                 Assert.Equal(expectedType, observableParameter.ParameterType);
diff --git a/Octokit.Tests.Conventions/TypeExtensions.cs b/Octokit.Tests.Conventions/TypeExtensions.cs
index ea7900a9..4028b26e 100644
--- a/Octokit.Tests.Conventions/TypeExtensions.cs
+++ b/Octokit.Tests.Conventions/TypeExtensions.cs
@@ -80,7 +80,7 @@ namespace Octokit.Tests.Conventions
             var observableInterface = observableClient.Assembly.GetType(observableClientName);
             if(observableInterface == null)
             {
-                throw new Exception("Cannot find observable interface "+observableClientName);
+                throw new InterfaceNotFoundException(observableClientName);
             }
             return observableInterface;
         }