Fix JobLoadException when using interface method as a background job

Closes HangfireIO#463

Author: odinserj

src/Hangfire.Core/Storage/InvocationData.cs

@@ -172,7 +172,14 @@ private static object DeserializeArgument(string argument, Type type)
 
         private static IEnumerable<MethodInfo> GetAllMethods(Type type)
         {
-            return type.IsInterface ? type.GetInterfaces().SelectMany(x => x.GetMethods()) : type.GetMethods();
+            var methods = new List<MethodInfo>(type.GetMethods());
+
+            if (type.IsInterface)
+            {
+                methods.AddRange(type.GetInterfaces().SelectMany(x => x.GetMethods()));
+            }
+
+            return methods;
         }
 
         private static MethodInfo GetNonOpenMatchingMethod(Type type, string name, Type[] parameterTypes)

tests/Hangfire.Core.Tests/Storage/InvocationDataFacts.cs

@@ -96,6 +96,20 @@ public void Deserialize_HandlesGenericMethods_WithOpenTypeParameters()
             Assert.False(job.Method.ContainsGenericParameters);
         }
 
+        [Fact]
+        public void Deserialize_HandlesMethodsDefinedInInterfaces()
+        {
+            var serializedData = new InvocationData(
+                typeof(IParent).AssemblyQualifiedName,
+                "Method",
+                JobHelper.ToJson(new string[0]),
+                JobHelper.ToJson(new string[0]));
+
+            var job = serializedData.Deserialize();
+
+            Assert.Equal(typeof(IParent), job.Type);
+        }
+
         [Fact]
         public void Deserialize_HandlesMethodsDefinedInParentInterfaces()
         {